<?xml version="1.0" encoding="utf-8" standalone="yes"?><rss version="2.0" xmlns:atom="http://www.w3.org/2005/Atom" xmlns:dc="http://purl.org/dc/elements/1.1/" xmlns:content="http://purl.org/rss/1.0/modules/content/" xmlns:media="http://search.yahoo.com/mrss/"><channel><title>Vex | FirewallSync</title><link>https://firewallsync.com/tags/vex/</link><description>Practical cybersecurity writing for engineering teams that ship fast.</description><language>en-us</language><image><url>https://firewallsync.com/icon-512.png</url><title>FirewallSync</title><link>https://firewallsync.com/</link></image><lastBuildDate>Fri, 06 Nov 2026 04:40:00 +0000</lastBuildDate><atom:link href="https://firewallsync.com/tags/vex/index.xml" rel="self" type="application/rss+xml"/><item><title>OpenVEX Products and Subcomponents: purl Matching Rules</title><link>https://firewallsync.com/posts/openvex-products-subcomponents-purl-matching-trivy/</link><guid>https://firewallsync.com/posts/openvex-products-subcomponents-purl-matching-trivy/</guid><pubDate>Fri, 06 Nov 2026 04:40:00 +0000</pubDate><dc:creator>Craig Leslie</dc:creator><category>AppSec &amp; APIs</category><description>An OpenVEX statement suppresses a finding only when its products, subcomponents and purls line up with what the scanner found. Here is how the go-vex library behind Trivy v0.76.2 matches them: versionless purls, qualifier subsets, subcomponent scoping, timestamp inheritance and which status wins, with a schema-valid example document and a tested Python port of the rules.</description><enclosure url="https://firewallsync.com/posts/openvex-products-subcomponents-purl-matching-trivy/cover_hu10637076205791324779.jpg" type="image/jpeg" length="0"/><media:content url="https://firewallsync.com/posts/openvex-products-subcomponents-purl-matching-trivy/cover_hu10637076205791324779.jpg" medium="image" type="image/jpeg" width="1200" height="630"/><content:encoded><![CDATA[<p><img src="https://firewallsync.com/posts/openvex-products-subcomponents-purl-matching-trivy/cover_hu10637076205791324779.jpg" alt="Three weathered wooden crates side by side on a white counter in front of a white brick wall" width="1200" height="630"></p><p>An OpenVEX statement only changes a scanner&rsquo;s output if its <strong>product</strong>, its <strong>subcomponents</strong> and the <strong>purls</strong> inside them match what the scanner found. In the go-vex library that Trivy v0.76.2 uses, the rules are short: the VEX purl is a pattern (no version means every version, and every qualifier it lists must be present), subcomponents narrow a statement to specific packages, and among matching statements the one with the newest timestamp wins. Most &ldquo;VEX didn&rsquo;t work&rdquo; tickets come down to one of those three.</p>
<p>This article is about the identifiers and the matching. For what the statuses and justifications mean, see <a href="/posts/vex-explained-what-a-not-affected-statement-means-and-how-to-read-one/">VEX explained</a>. For converting CycloneDX VEX to OpenVEX, see the <a href="/posts/cyclonedx-vex-analysis-state-justification-openvex-csaf-mapping/">CycloneDX VEX mapping</a>. For CSAF&rsquo;s product tree, see <a href="/posts/csaf-vex-product-tree-product-status-purl-sbom-matching/">CSAF VEX product_tree</a>.</p>
<h2 id="products-and-subcomponents-in-the-spec">Products and subcomponents in the spec</h2>
<p>The <a href="https://github.com/openvex/spec/blob/main/OPENVEX-SPEC.md">OpenVEX specification v0.2.0</a> defines a product as &ldquo;a logical unit representing a piece of software&rdquo;, broad enough that &ldquo;anything that can be described in a Software Bill of Materials (SBOM) can be thought of as a product.&rdquo; A subcomponent is &ldquo;any components possibly included in the product where the vulnerability originates.&rdquo; The spec adds that subcomponents &ldquo;SHOULD also list software identifiers and they SHOULD also be listed in the product SBOM.&rdquo;</p>
<p>Products and subcomponents share one structure, which the spec calls <code>Component</code>:</p>
<table>
  <thead>
      <tr>
          <th>Field</th>
          <th>Required</th>
          <th>What it holds</th>
      </tr>
  </thead>
  <tbody>
      <tr>
          <td><code>@id</code></td>
          <td>No</td>
          <td>An IRI for the component. A purl is a valid IRI, so <code>@id</code> can be a purl.</td>
      </tr>
      <tr>
          <td><code>identifiers</code></td>
          <td>No</td>
          <td>A map of identifier type to value. The spec lists <code>purl</code>, <code>cpe22</code> and <code>cpe23</code>, and recommends purls.</td>
      </tr>
      <tr>
          <td><code>hashes</code></td>
          <td>No</td>
          <td>A map of hash algorithm to digest, using IANA hash names.</td>
      </tr>
      <tr>
          <td><code>subcomponents</code></td>
          <td>No (products only)</td>
          <td>A list of components the statement is scoped to.</td>
      </tr>
  </tbody>
</table>
<p>All three identifying fields are optional, but the spec says a valid statement &ldquo;MUST identify a product.&rdquo; It also says the product should list &ldquo;as many software identifiers as possible to help VEX processors when matching the product.&rdquo;</p>
<p><code>products</code> itself is optional in a statement because it can be inherited from an encapsulating document, such as the subject of an in-toto attestation. Timestamps can be inherited too. The spec&rsquo;s inheritance rules are: a statement timestamp overrides the document timestamp, which overrides the encapsulating document&rsquo;s; a product ID in a statement overrides product data in the encapsulating document.</p>
<h2 id="how-go-vex-matches-a-statement">How go-vex matches a statement</h2>
<p>Trivy loads OpenVEX documents with <a href="https://github.com/openvex/go-vex">openvex/go-vex</a>, pinned to v0.2.9 in Trivy v0.76.2&rsquo;s <code>go.mod</code>. Its matching code is small enough to read in full. For a finding (CVE, product, optional subcomponent), a statement matches when all of these hold:</p>
<ol>
<li><strong>Vulnerability.</strong> The CVE ID equals the statement&rsquo;s <code>vulnerability.name</code>, its <code>@id</code>, or one of its <code>aliases</code>.</li>
<li><strong>Product.</strong> One entry in <code>products</code> matches the product identifier. A component matches if its <code>@id</code> equals the identifier exactly, or its <code>@id</code> is a purl that matches by the purl rules below, or any value in <code>identifiers</code> equals it (with purl matching for the <code>purl</code> key), or any value in <code>hashes</code> equals it.</li>
<li><strong>Subcomponent.</strong> If that product entry has no <code>subcomponents</code>, or the caller passed no subcomponent, the product match is enough. Otherwise one listed subcomponent must match the subcomponent identifier by the same component rules.</li>
</ol>
<h3 id="the-purl-rules">The purl rules</h3>
<p>go-vex&rsquo;s <code>PurlMatches(purl1, purl2)</code> treats the VEX purl as the general one and the scanned purl as the specific one:</p>
<table>
  <thead>
      <tr>
          <th>VEX purl</th>
          <th>Scanned purl</th>
          <th>Match?</th>
          <th>Rule</th>
      </tr>
  </thead>
  <tbody>
      <tr>
          <td><code>pkg:apk/alpine/git</code></td>
          <td><code>pkg:apk/alpine/git@2.43.0-r0?arch=x86_64</code></td>
          <td>Yes</td>
          <td>No version in the VEX purl matches any version</td>
      </tr>
      <tr>
          <td><code>pkg:apk/alpine/git@2.43.0-r0</code></td>
          <td><code>pkg:apk/alpine/git@2.43.0-r1</code></td>
          <td>No</td>
          <td>Versions must be equal when both are set</td>
      </tr>
      <tr>
          <td><code>pkg:apk/alpine/git@2.43.0-r0</code></td>
          <td><code>pkg:apk/alpine/git</code></td>
          <td>No</td>
          <td>A versioned VEX purl never matches a versionless scan result</td>
      </tr>
      <tr>
          <td><code>pkg:oci/app?repository_url=ghcr.io%2Facme%2Fapp</code></td>
          <td><code>pkg:oci/app?repository_url=ghcr.io%2Facme%2Fapp&amp;tag=v2</code></td>
          <td>Yes</td>
          <td>Extra qualifiers on the scanned side are ignored</td>
      </tr>
      <tr>
          <td><code>pkg:oci/app?repository_url=ghcr.io%2Facme%2Fapp</code></td>
          <td><code>pkg:oci/app</code></td>
          <td>No</td>
          <td>Every VEX qualifier must be present with the same value</td>
      </tr>
      <tr>
          <td><code>pkg:apk/alpine/git</code></td>
          <td><code>pkg:apk/alpine/git-daemon@2.43.0-r0</code></td>
          <td>No</td>
          <td>Type, namespace and name must be equal</td>
      </tr>
  </tbody>
</table>
<p>The function&rsquo;s own comment says &ldquo;Purl version ranges are not supported yet.&rdquo; A statement covering versions 1.0 to 1.4 needs either one purl per version or no version at all. Leaving the version off is the broadest possible statement, so use it only when you mean every version. Trivy&rsquo;s documentation notes that these matching rules come from a community discussion, not from the purl specification.</p>
<h3 id="which-statement-wins">Which statement wins</h3>
<p>go-vex collects every matching statement and sorts them by timestamp, using the document <code>timestamp</code> for any statement without its own. Trivy takes the last one. It removes the finding only if that statement&rsquo;s status is <code>not_affected</code> or <code>fixed</code>; <code>affected</code> and <code>under_investigation</code> leave the finding in the report.</p>
<p>This is why the spec&rsquo;s update example keeps the original document timestamp on the first statement when a second one is added. If you edit a document, bump <code>timestamp</code> and <code>version</code> at the document level, and the old statements lose their original time, the ordering of statements for the same CVE can change.</p>
<h2 id="a-tested-example">A tested example</h2>
<p>The document below has two statements for CVE-2024-32002 on a container image (the first <code>under_investigation</code> with its own timestamp, the second <code>not_affected</code> inheriting the newer document timestamp) and one statement for a Go service. It validates against the OpenVEX JSON schema (<code>openvex_json_schema.json</code> from the spec repository, checked with Python <code>jsonschema</code>).</p>
<div class="highlight"><pre tabindex="0" style="color:#f8f8f2;background-color:#272822;-moz-tab-size:4;-o-tab-size:4;tab-size:4;"><code class="language-json" data-lang="json"><span style="display:flex;"><span>{
</span></span><span style="display:flex;"><span>  <span style="color:#f92672">&#34;@context&#34;</span>: <span style="color:#e6db74">&#34;https://openvex.dev/ns/v0.2.0&#34;</span>,
</span></span><span style="display:flex;"><span>  <span style="color:#f92672">&#34;@id&#34;</span>: <span style="color:#e6db74">&#34;https://example.com/vex/app-2026-11-06&#34;</span>,
</span></span><span style="display:flex;"><span>  <span style="color:#f92672">&#34;author&#34;</span>: <span style="color:#e6db74">&#34;Example Security Team &lt;security@example.com&gt;&#34;</span>,
</span></span><span style="display:flex;"><span>  <span style="color:#f92672">&#34;timestamp&#34;</span>: <span style="color:#e6db74">&#34;2026-11-06T09:00:00Z&#34;</span>,
</span></span><span style="display:flex;"><span>  <span style="color:#f92672">&#34;version&#34;</span>: <span style="color:#ae81ff">2</span>,
</span></span><span style="display:flex;"><span>  <span style="color:#f92672">&#34;statements&#34;</span>: [
</span></span><span style="display:flex;"><span>    {
</span></span><span style="display:flex;"><span>      <span style="color:#f92672">&#34;vulnerability&#34;</span>: {<span style="color:#f92672">&#34;name&#34;</span>: <span style="color:#e6db74">&#34;CVE-2024-32002&#34;</span>},
</span></span><span style="display:flex;"><span>      <span style="color:#f92672">&#34;timestamp&#34;</span>: <span style="color:#e6db74">&#34;2026-11-01T10:00:00Z&#34;</span>,
</span></span><span style="display:flex;"><span>      <span style="color:#f92672">&#34;products&#34;</span>: [
</span></span><span style="display:flex;"><span>        {
</span></span><span style="display:flex;"><span>          <span style="color:#f92672">&#34;@id&#34;</span>: <span style="color:#e6db74">&#34;pkg:oci/app?repository_url=ghcr.io%2Facme%2Fapp&#34;</span>,
</span></span><span style="display:flex;"><span>          <span style="color:#f92672">&#34;subcomponents&#34;</span>: [{<span style="color:#f92672">&#34;@id&#34;</span>: <span style="color:#e6db74">&#34;pkg:apk/alpine/git&#34;</span>}]
</span></span><span style="display:flex;"><span>        }
</span></span><span style="display:flex;"><span>      ],
</span></span><span style="display:flex;"><span>      <span style="color:#f92672">&#34;status&#34;</span>: <span style="color:#e6db74">&#34;under_investigation&#34;</span>
</span></span><span style="display:flex;"><span>    },
</span></span><span style="display:flex;"><span>    {
</span></span><span style="display:flex;"><span>      <span style="color:#f92672">&#34;vulnerability&#34;</span>: {<span style="color:#f92672">&#34;name&#34;</span>: <span style="color:#e6db74">&#34;CVE-2024-32002&#34;</span>},
</span></span><span style="display:flex;"><span>      <span style="color:#f92672">&#34;products&#34;</span>: [
</span></span><span style="display:flex;"><span>        {
</span></span><span style="display:flex;"><span>          <span style="color:#f92672">&#34;@id&#34;</span>: <span style="color:#e6db74">&#34;pkg:oci/app?repository_url=ghcr.io%2Facme%2Fapp&#34;</span>,
</span></span><span style="display:flex;"><span>          <span style="color:#f92672">&#34;subcomponents&#34;</span>: [{<span style="color:#f92672">&#34;@id&#34;</span>: <span style="color:#e6db74">&#34;pkg:apk/alpine/git&#34;</span>}]
</span></span><span style="display:flex;"><span>        }
</span></span><span style="display:flex;"><span>      ],
</span></span><span style="display:flex;"><span>      <span style="color:#f92672">&#34;status&#34;</span>: <span style="color:#e6db74">&#34;not_affected&#34;</span>,
</span></span><span style="display:flex;"><span>      <span style="color:#f92672">&#34;justification&#34;</span>: <span style="color:#e6db74">&#34;vulnerable_code_not_in_execute_path&#34;</span>,
</span></span><span style="display:flex;"><span>      <span style="color:#f92672">&#34;status_notes&#34;</span>: <span style="color:#e6db74">&#34;git is installed for build-time use only; the runtime entrypoint never invokes git clone.&#34;</span>
</span></span><span style="display:flex;"><span>    },
</span></span><span style="display:flex;"><span>    {
</span></span><span style="display:flex;"><span>      <span style="color:#f92672">&#34;vulnerability&#34;</span>: {<span style="color:#f92672">&#34;name&#34;</span>: <span style="color:#e6db74">&#34;CVE-2023-0001&#34;</span>},
</span></span><span style="display:flex;"><span>      <span style="color:#f92672">&#34;products&#34;</span>: [
</span></span><span style="display:flex;"><span>        {
</span></span><span style="display:flex;"><span>          <span style="color:#f92672">&#34;@id&#34;</span>: <span style="color:#e6db74">&#34;pkg:golang/example.com/svc@v1.4.0&#34;</span>,
</span></span><span style="display:flex;"><span>          <span style="color:#f92672">&#34;subcomponents&#34;</span>: [{<span style="color:#f92672">&#34;@id&#34;</span>: <span style="color:#e6db74">&#34;pkg:golang/golang.org/x/net@v0.17.0&#34;</span>}]
</span></span><span style="display:flex;"><span>        }
</span></span><span style="display:flex;"><span>      ],
</span></span><span style="display:flex;"><span>      <span style="color:#f92672">&#34;status&#34;</span>: <span style="color:#e6db74">&#34;not_affected&#34;</span>,
</span></span><span style="display:flex;"><span>      <span style="color:#f92672">&#34;justification&#34;</span>: <span style="color:#e6db74">&#34;vulnerable_code_not_present&#34;</span>
</span></span><span style="display:flex;"><span>    }
</span></span><span style="display:flex;"><span>  ]
</span></span><span style="display:flex;"><span>}
</span></span></code></pre></div><p>The image, service names and CVE-2023-0001 statement are illustrative. To check the matching without a registry or a real image, we wrote a Python port of go-vex v0.2.9&rsquo;s <code>PurlMatches</code>, <code>Component.Matches</code>, <code>Product.Matches</code>, <code>Statement.Matches</code> and timestamp sort, using the <code>packageurl-python</code> parser, and ran it with Python 3 against the document. It is a port, not the Go library itself, so treat it as a reading aid. Output, with long purls shortened:</p>
<div class="highlight"><pre tabindex="0" style="color:#f8f8f2;background-color:#272822;-moz-tab-size:4;-o-tab-size:4;tab-size:4;"><code class="language-text" data-lang="text"><span style="display:flex;"><span>product                                    subcomponent                          result
</span></span><span style="display:flex;"><span>pkg:oci/app?repository_url=…%2Fapp         pkg:apk/alpine/git@2.43.0-r0?arch=…   2 matches, effective=not_affected
</span></span><span style="display:flex;"><span>pkg:oci/app?repository_url=…%2Fapp         pkg:apk/alpine/git-daemon@2.43.0-r0   no match
</span></span><span style="display:flex;"><span>pkg:oci/app?repository_url=…%2Fapp         (none)                                2 matches, effective=not_affected
</span></span><span style="display:flex;"><span>pkg:oci/app                                pkg:apk/alpine/git@2.43.0-r0          no match
</span></span><span style="display:flex;"><span>pkg:oci/app?repository_url=…%2Fapp&amp;tag=v2  pkg:apk/alpine/git@2.43.0-r0          2 matches, effective=not_affected
</span></span><span style="display:flex;"><span>pkg:golang/example.com/svc@v1.4.0          pkg:golang/golang.org/x/net@v0.17.0   1 match,  effective=not_affected
</span></span><span style="display:flex;"><span>pkg:golang/example.com/svc@v1.5.0          pkg:golang/golang.org/x/net@v0.17.0   no match
</span></span><span style="display:flex;"><span>pkg:golang/example.com/svc@v1.4.0          pkg:golang/golang.org/x/net@v0.18.0   no match
</span></span></code></pre></div><p>What the rows show:</p>
<ul>
<li><strong>Row 1:</strong> the versionless <code>pkg:apk/alpine/git</code> subcomponent covers the installed <code>git@2.43.0-r0</code>. Both statements match, and the <code>not_affected</code> one wins because it inherits the later document timestamp.</li>
<li><strong>Row 2:</strong> <code>git-daemon</code> is a different package name, so the statement does not cover it, even though it ships from the same source.</li>
<li><strong>Row 3:</strong> with no subcomponent passed, the product match alone is enough. Trivy does not hit this case for an image root (see below), but other consumers of go-vex may.</li>
<li><strong>Rows 4 and 5:</strong> the <code>repository_url</code> qualifier on the VEX side must be present on the scanned side. A scan purl without it fails; one with an extra <code>tag</code> qualifier passes.</li>
<li><strong>Rows 6 to 8:</strong> pinned versions on both product and subcomponent mean a new service release (v1.5.0) or a dependency bump (x/net v0.18.0) silently drops the statement. That is often what you want, since the reachability analysis was for that build, but it means the document needs updating each release.</li>
</ul>
<h2 id="how-trivy-applies-it-to-a-dependency-tree">How Trivy applies it to a dependency tree</h2>
<p>Trivy&rsquo;s VEX guide and its <code>filterVulnerabilities</code> code show how it feeds this matcher. For each finding it first asks whether the vulnerable package itself is a not-affected product (no subcomponent). If not, it walks up the dependency graph from the vulnerable package and asks, for each parent, whether &ldquo;parent as product, vulnerable package as subcomponent&rdquo; is not affected. The finding is removed only if no path reaches the root without passing a not-affected node.</p>
<p>Two consequences:</p>
<ul>
<li><strong>A statement on an intermediate dependency can suppress a finding, but only if every path goes through it.</strong> Trivy&rsquo;s documentation gives the example of Module C reached through both B and D: a VEX statement for B does not suppress the finding, because D might still be affected.</li>
<li><strong>A statement on the image with no subcomponents suppresses the CVE in every package in that image.</strong> Trivy&rsquo;s docs call this out and recommend subcomponents for &ldquo;reducing the risk of incorrect filtering.&rdquo;</li>
</ul>
<p>Trivy needs a purl on the scanned side. Its OpenVEX matcher returns nothing when the product has no purl, so cpe-only or hash-only VEX products are not matched by Trivy even though the spec allows them. Use the purls Trivy prints in its JSON report.</p>
<h2 id="writing-statements-that-match">Writing statements that match</h2>
<p>These are our recommendations, based on the rules above:</p>
<ol>
<li><strong>Copy purls from the scanner or SBOM output.</strong> Do not type them by hand; the type, namespace and name must match exactly. Our guide to <a href="/posts/cve-packageurl-purl-cve-json-5-2-affected-sbom-matching/">CVE packageURL and SBOM purls</a> covers common purl pitfalls.</li>
<li><strong>Always add subcomponents for image-level or application-level products.</strong> A product with no subcomponents is a blanket statement.</li>
<li><strong>Add a version only when the claim depends on the build.</strong> Reachability claims (<code>vulnerable_code_not_in_execute_path</code>) usually do. &ldquo;This package never ships the vulnerable file&rdquo; claims may not.</li>
<li><strong>Be sparing with qualifiers in the VEX purl.</strong> Each one is a requirement. <code>arch</code> is useful if only one architecture is unaffected; otherwise leave it out.</li>
<li><strong>Keep timestamps on old statements when you append new ones,</strong> and bump the document <code>version</code>. Use <code>status_notes</code> to record how the status was determined. Trivy does not read it, but reviewers do.</li>
<li><strong>Track the result.</strong> Our <a href="/posts/vulnerability-prioritization-workflow-cve-record-to-patch-ticket/">prioritization workflow</a> shows where a VEX decision sits between the CVE record and the ticket.</li>
</ol>
<h2 id="limits-of-this-article">Limits of this article</h2>
<ul>
<li>Matching behaviour is from go-vex v0.2.9 and Trivy v0.76.2 source and docs. Grype, vexctl and commercial scanners have their own matchers and may differ.</li>
<li>Our test used a Python port of the go-vex rules, not the Go library or a Trivy scan. The port follows the source shown in the references; differences in purl parsing between <code>packageurl-python</code> and <code>packageurl-go</code> are possible for unusual purls.</li>
<li>We did not cover OpenVEX attestations attached to OCI images (<code>--vex oci</code>) or VEX repositories.</li>
</ul>
<h2 id="sources-and-verification">Sources and verification</h2>
<table>
  <thead>
      <tr>
          <th>Important claim</th>
          <th>Source</th>
          <th>Status</th>
      </tr>
  </thead>
  <tbody>
      <tr>
          <td>Product, subcomponent, Component fields, identifier types, inheritance and update rules</td>
          <td><a href="https://github.com/openvex/spec/blob/main/OPENVEX-SPEC.md">OpenVEX specification v0.2.0</a></td>
          <td>Verified</td>
      </tr>
      <tr>
          <td>Example document is schema-valid</td>
          <td><a href="https://github.com/openvex/spec/blob/main/openvex_json_schema.json">openvex_json_schema.json</a>, checked with Python jsonschema</td>
          <td>Verified (tested)</td>
      </tr>
      <tr>
          <td>Trivy v0.76.2 uses go-vex v0.2.9; applies only not_affected and fixed; latest statement wins; requires a product purl</td>
          <td><a href="https://github.com/aquasecurity/trivy/blob/v0.76.2/pkg/vex/openvex.go">Trivy pkg/vex/openvex.go</a> and go.mod</td>
          <td>Verified</td>
      </tr>
      <tr>
          <td>Component, product, statement, vulnerability and purl matching rules; no version-range support; timestamp sort</td>
          <td><a href="https://github.com/openvex/go-vex/tree/v0.2.9/pkg/vex">go-vex v0.2.9 pkg/vex</a></td>
          <td>Verified</td>
      </tr>
      <tr>
          <td>Dependency-tree traversal and the multiple-paths rule</td>
          <td><a href="https://github.com/aquasecurity/trivy/blob/v0.76.2/docs/guide/supply-chain/vex/file.md">Trivy local VEX files guide</a> and pkg/vex/vex.go</td>
          <td>Verified</td>
      </tr>
      <tr>
          <td>Match results in the example table</td>
          <td>Python port of go-vex v0.2.9 rules, run against the example document</td>
          <td>Qualified: port, not the Go library</td>
      </tr>
  </tbody>
</table>
]]></content:encoded></item><item><title>CSAF VEX product_tree: Resolve Product IDs to SBOM purls</title><link>https://firewallsync.com/posts/csaf-vex-product-tree-product-status-purl-sbom-matching/</link><guid>https://firewallsync.com/posts/csaf-vex-product-tree-product-status-purl-sbom-matching/</guid><pubDate>Thu, 05 Nov 2026 04:30:00 +0000</pubDate><dc:creator>John Marshall</dc:creator><category>Security Operations</category><description>A CSAF VEX file never puts a purl next to a status. Product IDs in product_status point into the product_tree, often through relationships. Here is how to walk branches and relationships, collapse the eight status lists into four VEX answers, and join the result to a CycloneDX SBOM, with a tested Python script.</description><enclosure url="https://firewallsync.com/posts/csaf-vex-product-tree-product-status-purl-sbom-matching/cover_hu13121586183071927737.jpg" type="image/jpeg" length="0"/><media:content url="https://firewallsync.com/posts/csaf-vex-product-tree-product-status-purl-sbom-matching/cover_hu13121586183071927737.jpg" medium="image" type="image/jpeg" width="1200" height="630"/><content:encoded><![CDATA[<p><img src="https://firewallsync.com/posts/csaf-vex-product-tree-product-status-purl-sbom-matching/cover_hu13121586183071927737.jpg" alt="Thin bare tree branches crossing in a dense tangle against a flat grey-blue sky" width="1200" height="630"></p><p><strong>Scope.</strong> This is a field-level guide for engineers who consume vendor CSAF VEX files and need to apply them to their own SBOMs. We read the CSAF 2.0 prose and JSON schema in the OASIS CSAF TC&rsquo;s GitHub repository, Red Hat&rsquo;s July 2024 announcement of its CSAF VEX files, and Trivy&rsquo;s CSAF matcher and documentation at tag v0.76.1. The example document and the Python script below are ours; we validated the document against the CSAF 2.0 JSON schema and ran the script with Python 3.13. The script is illustrative, not a production matcher.</p>
<h2 id="the-short-answer">The short answer</h2>
<p>A CSAF VEX file never puts a purl next to a status. It says &ldquo;product ID <code>GW-4.2.1:LIB-1.8.0</code> is <code>known_not_affected</code>&rdquo;, and you have to work out what that ID is:</p>
<ol>
<li>Find the ID in the <code>product_tree</code>: at the end of a <code>branches</code> path, in <code>full_product_names</code>, or as the <code>full_product_name</code> of a <code>relationships</code> entry.</li>
<li>If it is a relationship, resolve both sides: <code>product_reference</code> (the component) and <code>relates_to_product_reference</code> (the product it sits in).</li>
<li>Read <code>product_identification_helper.purl</code> (or <code>cpe</code>) for each side.</li>
<li>Apply the status only when your SBOM contains the component <strong>and</strong> the parent matches the product you are assessing.</li>
<li>Collapse the eight <code>product_status</code> lists to the four VEX answers before you write anything to a ticket.</li>
</ol>
<p>The rest of this article goes through each step, shows a schema-valid example, and gives a script that does the join.</p>
<h2 id="what-the-vex-profile-requires">What the VEX profile requires</h2>
<p>CSAF 2.0 has been an OASIS Standard since 18 November 2022. The VEX profile is section 4.5. A document satisfies it when <code>/document/category</code> is <code>csaf_vex</code> and it contains:</p>
<ul>
<li>a <code>product_tree</code> &ldquo;which lists all products referenced later on in the CSAF document regardless of their state&rdquo;;</li>
<li><code>vulnerabilities</code>, each with <code>notes</code> and at least one of <code>cve</code> or <code>ids</code>;</li>
<li>at least one of the <code>fixed</code>, <code>known_affected</code>, <code>known_not_affected</code> or <code>under_investigation</code> lists.</li>
</ul>
<p>Two conditions are per product, and they are the ones consumers should check:</p>
<ul>
<li>Every product in <code>known_not_affected</code> needs an impact statement, either &ldquo;as machine readable flag in <code>/vulnerabilities[]/flags</code> or as human readable justification in <code>/vulnerabilities[]/threats</code>&rdquo; with <code>category</code> set to <code>impact</code>.</li>
<li>Every product in <code>known_affected</code> needs &ldquo;additional product specific information&rdquo; in <code>remediations</code> &ldquo;as an action statement&rdquo;. The categories <code>no_fix_planned</code> and <code>none_available</code> count.</li>
</ul>
<p>The five flag labels are the CISA justification codes: <code>component_not_present</code>, <code>vulnerable_code_not_present</code>, <code>vulnerable_code_cannot_be_controlled_by_adversary</code>, <code>vulnerable_code_not_in_execute_path</code> and <code>inline_mitigations_already_exist</code>. If you need the meaning of each one, the <a href="/posts/vex-explained-what-a-not-affected-statement-means-and-how-to-read-one/">VEX explainer</a> covers them. The <a href="/posts/cyclonedx-vex-analysis-state-justification-openvex-csaf-mapping/">CycloneDX VEX mapping guide</a> covers converting between CSAF and other VEX formats. This article is about something they do not cover: finding the products a CSAF statement actually refers to.</p>
<h2 id="step-1-walk-the-product-tree">Step 1: walk the product tree</h2>
<p>The <code>product_tree</code> can name products in three places. A consumer has to read all three.</p>
<table>
  <thead>
      <tr>
          <th>Where</th>
          <th>What it holds</th>
          <th>Product ID comes from</th>
      </tr>
  </thead>
  <tbody>
      <tr>
          <td><code>branches</code> (nested)</td>
          <td>A hierarchy such as <code>vendor</code> → <code>product_name</code> → <code>product_version</code>. A leaf branch has a <code>product</code> object.</td>
          <td><code>branches[]...product.product_id</code></td>
      </tr>
      <tr>
          <td><code>full_product_names</code></td>
          <td>Flat list of products with no hierarchy</td>
          <td><code>full_product_names[].product_id</code></td>
      </tr>
      <tr>
          <td><code>relationships</code></td>
          <td>A new product made of two existing ones, such as a library inside an image</td>
          <td><code>relationships[].full_product_name.product_id</code></td>
      </tr>
  </tbody>
</table>
<p>Every one of these is a &ldquo;full product name&rdquo;: <code>name</code> and <code>product_id</code> are required, and <code>product_identification_helper</code> is optional. That helper is where <code>purl</code>, <code>cpe</code>, hashes and SBOM URLs go. The CSAF schema only checks the purl against a loose pattern (<code>^pkg:[A-Za-z\.\-\+][A-Za-z0-9\.\-\+]*/.+</code>) and says it &ldquo;does not completely evaluate whether a PURL is valid&rdquo;, so validate purls yourself before matching on them.</p>
<p>There is also <code>product_groups</code>, which bundles product IDs under a group ID. Product status lists only hold product IDs, but <code>flags</code>, <code>threats</code> and <code>remediations</code> can reference groups through <code>group_ids</code>, so expand groups when you collect impact and action statements.</p>
<p>The spec recommends the <code>vendor</code> → <code>product_name</code> → <code>product_version</code> shape &ldquo;whenever possible to support the identification and matching of products on the consumer side&rdquo;. It also allows <code>product_version_range</code> branches, but recommends enumerating versions instead. If you meet a range branch, you need a version-range parser for whatever scheme it uses; the purl join below will not help.</p>
<h2 id="step-2-treat-relationships-as-component-in-product">Step 2: treat relationships as &ldquo;component in product&rdquo;</h2>
<p>A relationship has four required fields: <code>category</code>, <code>product_reference</code>, <code>relates_to_product_reference</code> and <code>full_product_name</code>. The categories are <code>default_component_of</code>, <code>external_component_of</code>, <code>installed_on</code>, <code>installed_with</code> and <code>optional_component_of</code>. The spec gives the reason relationships exist: a product may be &ldquo;vulnerable only when installed together with another&rdquo;, or you may need &ldquo;to describe operating system components&rdquo;.</p>
<p>This is the part consumers get wrong. In our example below, <code>LIB-1.8.0</code> is the library on its own and <code>GW-4.2.1:LIB-1.8.0</code> is &ldquo;libexample 1.8.0 as shipped in Example Gateway 4.2.1&rdquo;. A vendor that marks the second ID <code>known_not_affected</code> is saying the gateway does not reach the vulnerable code. It is not saying libexample 1.8.0 is safe everywhere. If your matcher resolves the relationship ID to the component purl alone, you will suppress the CVE for every other image that ships libexample 1.8.0. That is the false negative VEX is supposed to prevent.</p>
<p>The rule we use: for a relationship ID, apply the status only when the component purl matches a component in the SBOM <strong>and</strong> the parent purl matches the SBOM&rsquo;s subject (for CycloneDX, <code>metadata.component</code>).</p>
<p>Red Hat&rsquo;s VEX files are a real case of this structure. Red Hat publishes one CSAF VEX file per CVE. Its July 2024 announcement says each file has a <code>product_tree</code> object listing &ldquo;products, their components, and the relationships between them&rdquo;. In the general-availability release Red Hat &ldquo;extended the scope of the <code>purl</code> identifiers to unfixed components as well&rdquo; for rpm, oci and rpmmod components. In the October 2023 beta, only fixed components carried a purl. Check which one you are parsing.</p>
<h2 id="step-3-collapse-eight-status-lists-into-four-answers">Step 3: collapse eight status lists into four answers</h2>
<p>CSAF defines eight <code>product_status</code> lists. VEX consumers need four answers. The spec&rsquo;s own test for contradicting statuses (section 6.1.6) gives the grouping, and the sets &ldquo;MUST be pairwise disjoint&rdquo; within one vulnerability:</p>
<table>
  <thead>
      <tr>
          <th>VEX answer</th>
          <th>CSAF <code>product_status</code> lists</th>
          <th>What to do</th>
      </tr>
  </thead>
  <tbody>
      <tr>
          <td>Affected</td>
          <td><code>first_affected</code>, <code>known_affected</code>, <code>last_affected</code></td>
          <td>Open or keep the ticket. Read <code>remediations</code> for the action statement.</td>
      </tr>
      <tr>
          <td>Not affected</td>
          <td><code>known_not_affected</code></td>
          <td>Suppress for that product only, and keep the flag or impact text as evidence.</td>
      </tr>
      <tr>
          <td>Fixed</td>
          <td><code>first_fixed</code>, <code>fixed</code></td>
          <td>Close if you run that version. The spec says these versions &ldquo;may not be the recommended fixed versions&rdquo;.</td>
      </tr>
      <tr>
          <td>Under investigation</td>
          <td><code>under_investigation</code></td>
          <td>Keep the scanner finding and re-pull the document later.</td>
      </tr>
      <tr>
          <td>(none)</td>
          <td><code>recommended</code></td>
          <td>Not part of any contradiction group. The spec notes an issuer might recommend a version &ldquo;from any group - also from the affected group&rdquo;. Use it to choose an upgrade target, not to decide status.</td>
      </tr>
  </tbody>
</table>
<p>If you find one product ID in two groups for the same CVE, the document fails the CSAF mandatory test. Reject the statement for that product rather than picking one.</p>
<p>For affected products, the remediation categories tell you what kind of action is available: <code>vendor_fix</code>, <code>workaround</code>, <code>mitigation</code>, <code>none_available</code> or <code>no_fix_planned</code>. <code>vendor_fix</code> cannot be combined with <code>none_available</code> or <code>no_fix_planned</code> for the same product.</p>
<h2 id="a-schema-valid-example">A schema-valid example</h2>
<p>This document is ours, written for this article. It has one product version where a library is not reachable and a later version where it was updated. It passes validation against the CSAF 2.0 JSON schema from the OASIS repository (Python <code>jsonschema</code>, Draft 2020-12, format checks on; 0 errors). Schema validation does not run CSAF&rsquo;s mandatory tests, so it does not prove the profile rules are met. We checked those by hand.</p>
<div class="highlight"><pre tabindex="0" style="color:#f8f8f2;background-color:#272822;-moz-tab-size:4;-o-tab-size:4;tab-size:4;"><code class="language-json" data-lang="json"><span style="display:flex;"><span>{
</span></span><span style="display:flex;"><span>  <span style="color:#f92672">&#34;document&#34;</span>: {
</span></span><span style="display:flex;"><span>    <span style="color:#f92672">&#34;category&#34;</span>: <span style="color:#e6db74">&#34;csaf_vex&#34;</span>,
</span></span><span style="display:flex;"><span>    <span style="color:#f92672">&#34;csaf_version&#34;</span>: <span style="color:#e6db74">&#34;2.0&#34;</span>,
</span></span><span style="display:flex;"><span>    <span style="color:#f92672">&#34;publisher&#34;</span>: {<span style="color:#f92672">&#34;category&#34;</span>: <span style="color:#e6db74">&#34;vendor&#34;</span>, <span style="color:#f92672">&#34;name&#34;</span>: <span style="color:#e6db74">&#34;Example Vendor&#34;</span>, <span style="color:#f92672">&#34;namespace&#34;</span>: <span style="color:#e6db74">&#34;https://vendor.example&#34;</span>},
</span></span><span style="display:flex;"><span>    <span style="color:#f92672">&#34;title&#34;</span>: <span style="color:#e6db74">&#34;Example Gateway: CVE-2099-0001 in libexample&#34;</span>,
</span></span><span style="display:flex;"><span>    <span style="color:#f92672">&#34;tracking&#34;</span>: {<span style="color:#f92672">&#34;id&#34;</span>: <span style="color:#e6db74">&#34;EXV-2099-0001&#34;</span>, <span style="color:#f92672">&#34;status&#34;</span>: <span style="color:#e6db74">&#34;final&#34;</span>, <span style="color:#f92672">&#34;version&#34;</span>: <span style="color:#e6db74">&#34;2&#34;</span>, <span style="color:#f92672">&#34;...&#34;</span>: <span style="color:#e6db74">&#34;...&#34;</span>}
</span></span><span style="display:flex;"><span>  },
</span></span><span style="display:flex;"><span>  <span style="color:#f92672">&#34;product_tree&#34;</span>: {
</span></span><span style="display:flex;"><span>    <span style="color:#f92672">&#34;branches&#34;</span>: [{<span style="color:#f92672">&#34;category&#34;</span>: <span style="color:#e6db74">&#34;vendor&#34;</span>, <span style="color:#f92672">&#34;name&#34;</span>: <span style="color:#e6db74">&#34;Example Vendor&#34;</span>, <span style="color:#f92672">&#34;branches&#34;</span>: [
</span></span><span style="display:flex;"><span>      {<span style="color:#f92672">&#34;category&#34;</span>: <span style="color:#e6db74">&#34;product_name&#34;</span>, <span style="color:#f92672">&#34;name&#34;</span>: <span style="color:#e6db74">&#34;Example Gateway&#34;</span>, <span style="color:#f92672">&#34;branches&#34;</span>: [
</span></span><span style="display:flex;"><span>        {<span style="color:#f92672">&#34;category&#34;</span>: <span style="color:#e6db74">&#34;product_version&#34;</span>, <span style="color:#f92672">&#34;name&#34;</span>: <span style="color:#e6db74">&#34;4.2.1&#34;</span>,
</span></span><span style="display:flex;"><span>         <span style="color:#f92672">&#34;product&#34;</span>: {<span style="color:#f92672">&#34;name&#34;</span>: <span style="color:#e6db74">&#34;Example Gateway 4.2.1&#34;</span>, <span style="color:#f92672">&#34;product_id&#34;</span>: <span style="color:#e6db74">&#34;GW-4.2.1&#34;</span>,
</span></span><span style="display:flex;"><span>           <span style="color:#f92672">&#34;product_identification_helper&#34;</span>: {<span style="color:#f92672">&#34;purl&#34;</span>: <span style="color:#e6db74">&#34;pkg:oci/example-gateway@sha256%3A1111?tag=4.2.1&#34;</span>}}}
</span></span><span style="display:flex;"><span>      ]},
</span></span><span style="display:flex;"><span>      {<span style="color:#f92672">&#34;category&#34;</span>: <span style="color:#e6db74">&#34;product_name&#34;</span>, <span style="color:#f92672">&#34;name&#34;</span>: <span style="color:#e6db74">&#34;libexample&#34;</span>, <span style="color:#f92672">&#34;branches&#34;</span>: [
</span></span><span style="display:flex;"><span>        {<span style="color:#f92672">&#34;category&#34;</span>: <span style="color:#e6db74">&#34;product_version&#34;</span>, <span style="color:#f92672">&#34;name&#34;</span>: <span style="color:#e6db74">&#34;1.8.0&#34;</span>,
</span></span><span style="display:flex;"><span>         <span style="color:#f92672">&#34;product&#34;</span>: {<span style="color:#f92672">&#34;name&#34;</span>: <span style="color:#e6db74">&#34;libexample 1.8.0&#34;</span>, <span style="color:#f92672">&#34;product_id&#34;</span>: <span style="color:#e6db74">&#34;LIB-1.8.0&#34;</span>,
</span></span><span style="display:flex;"><span>           <span style="color:#f92672">&#34;product_identification_helper&#34;</span>: {<span style="color:#f92672">&#34;purl&#34;</span>: <span style="color:#e6db74">&#34;pkg:deb/debian/libexample@1.8.0-1&#34;</span>}}}
</span></span><span style="display:flex;"><span>      ]}
</span></span><span style="display:flex;"><span>    ]}],
</span></span><span style="display:flex;"><span>    <span style="color:#f92672">&#34;relationships&#34;</span>: [
</span></span><span style="display:flex;"><span>      {<span style="color:#f92672">&#34;category&#34;</span>: <span style="color:#e6db74">&#34;default_component_of&#34;</span>,
</span></span><span style="display:flex;"><span>       <span style="color:#f92672">&#34;product_reference&#34;</span>: <span style="color:#e6db74">&#34;LIB-1.8.0&#34;</span>,
</span></span><span style="display:flex;"><span>       <span style="color:#f92672">&#34;relates_to_product_reference&#34;</span>: <span style="color:#e6db74">&#34;GW-4.2.1&#34;</span>,
</span></span><span style="display:flex;"><span>       <span style="color:#f92672">&#34;full_product_name&#34;</span>: {<span style="color:#f92672">&#34;name&#34;</span>: <span style="color:#e6db74">&#34;libexample 1.8.0 in Example Gateway 4.2.1&#34;</span>,
</span></span><span style="display:flex;"><span>                             <span style="color:#f92672">&#34;product_id&#34;</span>: <span style="color:#e6db74">&#34;GW-4.2.1:LIB-1.8.0&#34;</span>}}
</span></span><span style="display:flex;"><span>    ]
</span></span><span style="display:flex;"><span>  },
</span></span><span style="display:flex;"><span>  <span style="color:#f92672">&#34;vulnerabilities&#34;</span>: [{
</span></span><span style="display:flex;"><span>    <span style="color:#f92672">&#34;cve&#34;</span>: <span style="color:#e6db74">&#34;CVE-2099-0001&#34;</span>,
</span></span><span style="display:flex;"><span>    <span style="color:#f92672">&#34;notes&#34;</span>: [{<span style="color:#f92672">&#34;category&#34;</span>: <span style="color:#e6db74">&#34;description&#34;</span>, <span style="color:#f92672">&#34;text&#34;</span>: <span style="color:#e6db74">&#34;Illustrative vulnerability in libexample&#39;s XML parser.&#34;</span>}],
</span></span><span style="display:flex;"><span>    <span style="color:#f92672">&#34;product_status&#34;</span>: {<span style="color:#f92672">&#34;known_not_affected&#34;</span>: [<span style="color:#e6db74">&#34;GW-4.2.1:LIB-1.8.0&#34;</span>], <span style="color:#f92672">&#34;fixed&#34;</span>: [<span style="color:#e6db74">&#34;GW-4.3.0:LIB-1.8.2&#34;</span>]},
</span></span><span style="display:flex;"><span>    <span style="color:#f92672">&#34;flags&#34;</span>: [{<span style="color:#f92672">&#34;label&#34;</span>: <span style="color:#e6db74">&#34;vulnerable_code_not_in_execute_path&#34;</span>, <span style="color:#f92672">&#34;product_ids&#34;</span>: [<span style="color:#e6db74">&#34;GW-4.2.1:LIB-1.8.0&#34;</span>]}],
</span></span><span style="display:flex;"><span>    <span style="color:#f92672">&#34;threats&#34;</span>: [{<span style="color:#f92672">&#34;category&#34;</span>: <span style="color:#e6db74">&#34;impact&#34;</span>, <span style="color:#f92672">&#34;details&#34;</span>: <span style="color:#e6db74">&#34;Example Gateway never calls the XML parser in libexample.&#34;</span>,
</span></span><span style="display:flex;"><span>                 <span style="color:#f92672">&#34;product_ids&#34;</span>: [<span style="color:#e6db74">&#34;GW-4.2.1:LIB-1.8.0&#34;</span>]}]
</span></span><span style="display:flex;"><span>  }]
</span></span><span style="display:flex;"><span>}
</span></span></code></pre></div><p>The excerpt trims the tracking block and the 4.3.0 / 1.8.2 branches and relationship, which follow the same pattern. The CVE ID is a placeholder.</p>
<h2 id="step-4-join-to-the-sbom">Step 4: join to the SBOM</h2>
<p>The script resolves every product ID in <code>product_status</code> to purls, follows relationships, and checks both sides against a CycloneDX SBOM. For purl comparison it uses the matching rules Trivy documents, which Trivy itself notes &ldquo;are not formally defined within the current official PURL specification&rdquo;: a VEX purl without a version matches every version; every qualifier in the VEX purl must be present in the SBOM purl; extra SBOM qualifiers are ignored.</p>
<div class="highlight"><pre tabindex="0" style="color:#f8f8f2;background-color:#272822;-moz-tab-size:4;-o-tab-size:4;tab-size:4;"><code class="language-python" data-lang="python"><span style="display:flex;"><span><span style="color:#75715e">#!/usr/bin/env python3</span>
</span></span><span style="display:flex;"><span><span style="color:#e6db74">&#34;&#34;&#34;Resolve CSAF VEX product_status entries to purls and join them to a CycloneDX SBOM.
</span></span></span><span style="display:flex;"><span><span style="color:#e6db74">Illustrative: purl matching follows the rules in purl_match(); no version-range logic.&#34;&#34;&#34;</span>
</span></span><span style="display:flex;"><span><span style="color:#f92672">import</span> json<span style="color:#f92672">,</span> sys
</span></span><span style="display:flex;"><span><span style="color:#f92672">from</span> urllib.parse <span style="color:#f92672">import</span> unquote
</span></span><span style="display:flex;"><span>
</span></span><span style="display:flex;"><span><span style="color:#66d9ef">def</span> <span style="color:#a6e22e">parse</span>(p):
</span></span><span style="display:flex;"><span>    <span style="color:#e6db74">&#34;&#34;&#34;Split a purl into (type/namespace/name, version or None, qualifiers dict). Subpath ignored.&#34;&#34;&#34;</span>
</span></span><span style="display:flex;"><span>    p <span style="color:#f92672">=</span> p<span style="color:#f92672">.</span>split(<span style="color:#e6db74">&#34;#&#34;</span>)[<span style="color:#ae81ff">0</span>]
</span></span><span style="display:flex;"><span>    core, _, q <span style="color:#f92672">=</span> p<span style="color:#f92672">.</span>partition(<span style="color:#e6db74">&#34;?&#34;</span>)
</span></span><span style="display:flex;"><span>    quals <span style="color:#f92672">=</span> dict(kv<span style="color:#f92672">.</span>split(<span style="color:#e6db74">&#34;=&#34;</span>, <span style="color:#ae81ff">1</span>) <span style="color:#66d9ef">for</span> kv <span style="color:#f92672">in</span> q<span style="color:#f92672">.</span>split(<span style="color:#e6db74">&#34;&amp;&#34;</span>) <span style="color:#66d9ef">if</span> <span style="color:#e6db74">&#34;=&#34;</span> <span style="color:#f92672">in</span> kv)
</span></span><span style="display:flex;"><span>    path, _, ver <span style="color:#f92672">=</span> core<span style="color:#f92672">.</span>rpartition(<span style="color:#e6db74">&#34;@&#34;</span>) <span style="color:#66d9ef">if</span> <span style="color:#e6db74">&#34;@&#34;</span> <span style="color:#f92672">in</span> core<span style="color:#f92672">.</span>rsplit(<span style="color:#e6db74">&#34;/&#34;</span>, <span style="color:#ae81ff">1</span>)[<span style="color:#f92672">-</span><span style="color:#ae81ff">1</span>] <span style="color:#66d9ef">else</span> (core, <span style="color:#e6db74">&#34;&#34;</span>, <span style="color:#e6db74">&#34;&#34;</span>)
</span></span><span style="display:flex;"><span>    <span style="color:#66d9ef">return</span> unquote(path)<span style="color:#f92672">.</span>lower(), unquote(ver) <span style="color:#f92672">or</span> <span style="color:#66d9ef">None</span>, {k<span style="color:#f92672">.</span>lower(): unquote(v) <span style="color:#66d9ef">for</span> k, v <span style="color:#f92672">in</span> quals<span style="color:#f92672">.</span>items()}
</span></span><span style="display:flex;"><span>
</span></span><span style="display:flex;"><span><span style="color:#66d9ef">def</span> <span style="color:#a6e22e">purl_match</span>(vex_purl, sbom_purl):
</span></span><span style="display:flex;"><span>    <span style="color:#e6db74">&#34;&#34;&#34;Community matching rules (as documented by Trivy): a VEX purl without a version matches
</span></span></span><span style="display:flex;"><span><span style="color:#e6db74">    every version; VEX qualifiers must all be present in the SBOM purl; extra SBOM qualifiers are ignored.&#34;&#34;&#34;</span>
</span></span><span style="display:flex;"><span>    vp, vv, vq <span style="color:#f92672">=</span> parse(vex_purl)
</span></span><span style="display:flex;"><span>    sp, sv, sq <span style="color:#f92672">=</span> parse(sbom_purl)
</span></span><span style="display:flex;"><span>    <span style="color:#66d9ef">return</span> vp <span style="color:#f92672">==</span> sp <span style="color:#f92672">and</span> (vv <span style="color:#f92672">is</span> <span style="color:#66d9ef">None</span> <span style="color:#f92672">or</span> vv <span style="color:#f92672">==</span> sv) <span style="color:#f92672">and</span> all(sq<span style="color:#f92672">.</span>get(k) <span style="color:#f92672">==</span> v <span style="color:#66d9ef">for</span> k, v <span style="color:#f92672">in</span> vq<span style="color:#f92672">.</span>items())
</span></span><span style="display:flex;"><span>
</span></span><span style="display:flex;"><span><span style="color:#66d9ef">def</span> <span style="color:#a6e22e">walk_branches</span>(branches, out):
</span></span><span style="display:flex;"><span>    <span style="color:#66d9ef">for</span> b <span style="color:#f92672">in</span> branches <span style="color:#f92672">or</span> []:
</span></span><span style="display:flex;"><span>        <span style="color:#66d9ef">if</span> <span style="color:#e6db74">&#34;product&#34;</span> <span style="color:#f92672">in</span> b:
</span></span><span style="display:flex;"><span>            fpn <span style="color:#f92672">=</span> b[<span style="color:#e6db74">&#34;product&#34;</span>]
</span></span><span style="display:flex;"><span>            out[fpn[<span style="color:#e6db74">&#34;product_id&#34;</span>]] <span style="color:#f92672">=</span> fpn<span style="color:#f92672">.</span>get(<span style="color:#e6db74">&#34;product_identification_helper&#34;</span>, {})<span style="color:#f92672">.</span>get(<span style="color:#e6db74">&#34;purl&#34;</span>)
</span></span><span style="display:flex;"><span>        walk_branches(b<span style="color:#f92672">.</span>get(<span style="color:#e6db74">&#34;branches&#34;</span>), out)
</span></span><span style="display:flex;"><span>
</span></span><span style="display:flex;"><span><span style="color:#66d9ef">def</span> <span style="color:#a6e22e">load_products</span>(doc):
</span></span><span style="display:flex;"><span>    tree <span style="color:#f92672">=</span> doc[<span style="color:#e6db74">&#34;product_tree&#34;</span>]
</span></span><span style="display:flex;"><span>    purls <span style="color:#f92672">=</span> {}
</span></span><span style="display:flex;"><span>    walk_branches(tree<span style="color:#f92672">.</span>get(<span style="color:#e6db74">&#34;branches&#34;</span>), purls)
</span></span><span style="display:flex;"><span>    <span style="color:#66d9ef">for</span> fpn <span style="color:#f92672">in</span> tree<span style="color:#f92672">.</span>get(<span style="color:#e6db74">&#34;full_product_names&#34;</span>, []):
</span></span><span style="display:flex;"><span>        purls[fpn[<span style="color:#e6db74">&#34;product_id&#34;</span>]] <span style="color:#f92672">=</span> fpn<span style="color:#f92672">.</span>get(<span style="color:#e6db74">&#34;product_identification_helper&#34;</span>, {})<span style="color:#f92672">.</span>get(<span style="color:#e6db74">&#34;purl&#34;</span>)
</span></span><span style="display:flex;"><span>    rels <span style="color:#f92672">=</span> {}
</span></span><span style="display:flex;"><span>    <span style="color:#66d9ef">for</span> r <span style="color:#f92672">in</span> tree<span style="color:#f92672">.</span>get(<span style="color:#e6db74">&#34;relationships&#34;</span>, []):
</span></span><span style="display:flex;"><span>        rels[r[<span style="color:#e6db74">&#34;full_product_name&#34;</span>][<span style="color:#e6db74">&#34;product_id&#34;</span>]] <span style="color:#f92672">=</span> (
</span></span><span style="display:flex;"><span>            r[<span style="color:#e6db74">&#34;category&#34;</span>], r[<span style="color:#e6db74">&#34;product_reference&#34;</span>], r[<span style="color:#e6db74">&#34;relates_to_product_reference&#34;</span>])
</span></span><span style="display:flex;"><span>    groups <span style="color:#f92672">=</span> {g[<span style="color:#e6db74">&#34;group_id&#34;</span>]: g[<span style="color:#e6db74">&#34;product_ids&#34;</span>] <span style="color:#66d9ef">for</span> g <span style="color:#f92672">in</span> tree<span style="color:#f92672">.</span>get(<span style="color:#e6db74">&#34;product_groups&#34;</span>, [])}
</span></span><span style="display:flex;"><span>    <span style="color:#66d9ef">return</span> purls, rels, groups
</span></span><span style="display:flex;"><span>
</span></span><span style="display:flex;"><span><span style="color:#66d9ef">def</span> <span style="color:#a6e22e">main</span>(vex_path, sbom_path):
</span></span><span style="display:flex;"><span>    doc <span style="color:#f92672">=</span> json<span style="color:#f92672">.</span>load(open(vex_path))
</span></span><span style="display:flex;"><span>    <span style="color:#66d9ef">assert</span> doc[<span style="color:#e6db74">&#34;document&#34;</span>][<span style="color:#e6db74">&#34;category&#34;</span>] <span style="color:#f92672">==</span> <span style="color:#e6db74">&#34;csaf_vex&#34;</span>, <span style="color:#e6db74">&#34;not a VEX profile document&#34;</span>
</span></span><span style="display:flex;"><span>    purls, rels, groups <span style="color:#f92672">=</span> load_products(doc)
</span></span><span style="display:flex;"><span>    sbom <span style="color:#f92672">=</span> json<span style="color:#f92672">.</span>load(open(sbom_path))
</span></span><span style="display:flex;"><span>    parent <span style="color:#f92672">=</span> sbom[<span style="color:#e6db74">&#34;metadata&#34;</span>][<span style="color:#e6db74">&#34;component&#34;</span>][<span style="color:#e6db74">&#34;purl&#34;</span>]
</span></span><span style="display:flex;"><span>    inventory <span style="color:#f92672">=</span> [c[<span style="color:#e6db74">&#34;purl&#34;</span>] <span style="color:#66d9ef">for</span> c <span style="color:#f92672">in</span> sbom<span style="color:#f92672">.</span>get(<span style="color:#e6db74">&#34;components&#34;</span>, []) <span style="color:#66d9ef">if</span> c<span style="color:#f92672">.</span>get(<span style="color:#e6db74">&#34;purl&#34;</span>)]
</span></span><span style="display:flex;"><span>    in_sbom <span style="color:#f92672">=</span> <span style="color:#66d9ef">lambda</span> vex_purl: any(purl_match(vex_purl, s) <span style="color:#66d9ef">for</span> s <span style="color:#f92672">in</span> inventory)
</span></span><span style="display:flex;"><span>
</span></span><span style="display:flex;"><span>    <span style="color:#66d9ef">for</span> v <span style="color:#f92672">in</span> doc[<span style="color:#e6db74">&#34;vulnerabilities&#34;</span>]:
</span></span><span style="display:flex;"><span>        flags <span style="color:#f92672">=</span> {pid: f[<span style="color:#e6db74">&#34;label&#34;</span>] <span style="color:#66d9ef">for</span> f <span style="color:#f92672">in</span> v<span style="color:#f92672">.</span>get(<span style="color:#e6db74">&#34;flags&#34;</span>, [])
</span></span><span style="display:flex;"><span>                 <span style="color:#66d9ef">for</span> pid <span style="color:#f92672">in</span> f<span style="color:#f92672">.</span>get(<span style="color:#e6db74">&#34;product_ids&#34;</span>, []) <span style="color:#f92672">+</span> sum((groups[g] <span style="color:#66d9ef">for</span> g <span style="color:#f92672">in</span> f<span style="color:#f92672">.</span>get(<span style="color:#e6db74">&#34;group_ids&#34;</span>, [])), [])}
</span></span><span style="display:flex;"><span>        <span style="color:#66d9ef">for</span> status, pids <span style="color:#f92672">in</span> v<span style="color:#f92672">.</span>get(<span style="color:#e6db74">&#34;product_status&#34;</span>, {})<span style="color:#f92672">.</span>items():
</span></span><span style="display:flex;"><span>            <span style="color:#66d9ef">for</span> pid <span style="color:#f92672">in</span> pids:
</span></span><span style="display:flex;"><span>                <span style="color:#66d9ef">if</span> pid <span style="color:#f92672">in</span> rels:                      <span style="color:#75715e"># component-in-product: match BOTH sides</span>
</span></span><span style="display:flex;"><span>                    cat, comp, prod <span style="color:#f92672">=</span> rels[pid]
</span></span><span style="display:flex;"><span>                    comp_p, prod_p <span style="color:#f92672">=</span> purls<span style="color:#f92672">.</span>get(comp), purls<span style="color:#f92672">.</span>get(prod)
</span></span><span style="display:flex;"><span>                    hit <span style="color:#f92672">=</span> bool(comp_p <span style="color:#f92672">and</span> prod_p <span style="color:#f92672">and</span> purl_match(prod_p, parent) <span style="color:#f92672">and</span> in_sbom(comp_p))
</span></span><span style="display:flex;"><span>                    target <span style="color:#f92672">=</span> <span style="color:#e6db74">f</span><span style="color:#e6db74">&#34;</span><span style="color:#e6db74">{</span>comp_p<span style="color:#e6db74">}</span><span style="color:#e6db74"> </span><span style="color:#e6db74">{</span>cat<span style="color:#e6db74">}</span><span style="color:#e6db74"> </span><span style="color:#e6db74">{</span>prod_p<span style="color:#e6db74">}</span><span style="color:#e6db74">&#34;</span>
</span></span><span style="display:flex;"><span>                <span style="color:#66d9ef">else</span>:                                <span style="color:#75715e"># standalone product</span>
</span></span><span style="display:flex;"><span>                    p <span style="color:#f92672">=</span> purls<span style="color:#f92672">.</span>get(pid)
</span></span><span style="display:flex;"><span>                    hit <span style="color:#f92672">=</span> bool(p <span style="color:#f92672">and</span> (in_sbom(p) <span style="color:#f92672">or</span> purl_match(p, parent)))
</span></span><span style="display:flex;"><span>                    target <span style="color:#f92672">=</span> p
</span></span><span style="display:flex;"><span>                print(<span style="color:#e6db74">f</span><span style="color:#e6db74">&#34;</span><span style="color:#e6db74">{</span>v<span style="color:#f92672">.</span>get(<span style="color:#e6db74">&#39;cve&#39;</span>)<span style="color:#e6db74">}</span><span style="color:#ae81ff">\t</span><span style="color:#e6db74">{</span>status<span style="color:#e6db74">}</span><span style="color:#ae81ff">\t</span><span style="color:#e6db74">{</span>flags<span style="color:#f92672">.</span>get(pid, <span style="color:#e6db74">&#39;-&#39;</span>)<span style="color:#e6db74">}</span><span style="color:#ae81ff">\t</span><span style="color:#e6db74">{</span><span style="color:#e6db74">&#39;MATCH&#39;</span> <span style="color:#66d9ef">if</span> hit <span style="color:#66d9ef">else</span> <span style="color:#e6db74">&#39;no match&#39;</span><span style="color:#e6db74">}</span><span style="color:#ae81ff">\t</span><span style="color:#e6db74">{</span>target<span style="color:#e6db74">}</span><span style="color:#e6db74">&#34;</span>)
</span></span><span style="display:flex;"><span>
</span></span><span style="display:flex;"><span><span style="color:#66d9ef">if</span> __name__ <span style="color:#f92672">==</span> <span style="color:#e6db74">&#34;__main__&#34;</span>:
</span></span><span style="display:flex;"><span>    main(<span style="color:#f92672">*</span>sys<span style="color:#f92672">.</span>argv[<span style="color:#ae81ff">1</span>:<span style="color:#ae81ff">3</span>])
</span></span></code></pre></div><h3 id="test-run">Test run</h3>
<p>We ran it (<code>python3 -I csaf_vex_join.py vex.json sbom.cdx.json</code>) against the full example document and three small CycloneDX 1.6 SBOMs.</p>
<p><strong>SBOM 1</strong>, image 4.2.1 (<code>metadata.component.purl</code> = <code>pkg:oci/example-gateway@sha256%3A1111?tag=4.2.1</code>), containing <code>pkg:deb/debian/libexample@1.8.0-1?arch=amd64&amp;distro=debian-12</code>:</p>
<div class="highlight"><pre tabindex="0" style="color:#f8f8f2;background-color:#272822;-moz-tab-size:4;-o-tab-size:4;tab-size:4;"><code class="language-text" data-lang="text"><span style="display:flex;"><span>CVE-2099-0001  known_not_affected  vulnerable_code_not_in_execute_path  MATCH     pkg:deb/debian/libexample@1.8.0-1 default_component_of pkg:oci/example-gateway@sha256%3A1111?tag=4.2.1
</span></span><span style="display:flex;"><span>CVE-2099-0001  fixed               -                                    no match  pkg:deb/debian/libexample@1.8.2-1 default_component_of pkg:oci/example-gateway@sha256%3A2222?tag=4.3.0
</span></span></code></pre></div><p>The SBOM&rsquo;s extra <code>arch</code> and <code>distro</code> qualifiers did not block the match, because the VEX purl has none.</p>
<p><strong>SBOM 2</strong>, image 4.3.0 with libexample 1.8.2: the results flip. The <code>fixed</code> statement matches and the <code>known_not_affected</code> one does not.</p>
<p><strong>SBOM 3</strong>, the 4.2.1 SBOM again, but with the VEX component purl changed to <code>...libexample@1.8.0-1?arch=arm64</code>: <code>no match</code>, because the VEX purl now requires a qualifier value the SBOM lacks.</p>
<p>What the script does not do: version ranges (<code>product_version_range</code>), CPE-only products, hashes, <code>product_groups</code> in status lists (the schema does not allow them there), or the mandatory-test checks. It also prints matches and nothing else; it does not decide what to do with a CVE your scanner found but the VEX file does not mention.</p>
<h2 id="how-trivy-applies-csaf-vex">How Trivy applies CSAF VEX</h2>
<p>Trivy is a common place engineers first meet CSAF VEX. At tag v0.76.1, its documentation says CSAF works for container images, filesystems, code repositories, VM images, Kubernetes and SBOM targets, passed with <code>--vex</code>. Its matcher (<code>pkg/vex/csaf.go</code>) shows three things worth knowing:</p>
<ul>
<li><strong>Only two statuses act.</strong> The status map holds <code>known_not_affected</code> and <code>fixed</code>. A match on either filters the finding. <code>known_affected</code> and <code>under_investigation</code> statements never change the result.</li>
<li><strong>Matching is by purl.</strong> If the detected package has no purl, or the vulnerability has no <code>product_status</code>, nothing is filtered.</li>
<li><strong>Relationship categories are not distinguished.</strong> The documentation says &ldquo;the specified relationship category is not taken into account&rdquo; and that <code>default_component_of</code>, <code>installed_on</code> and <code>installed_with</code> &ldquo;are treated internally as <code>depends_on</code>&rdquo;. For a relationship, the code requires the parent purl to match a product higher in the dependency tree (such as the scanned image) and the component purl to match the sub-component, which is the both-sides rule from Step 2. <code>external_component_of</code> and <code>optional_component_of</code> relationships are skipped. A status on a plain product ID, with no relationship, is matched against the package&rsquo;s own purl, so it applies wherever that package appears.</li>
</ul>
<p>So if a vendor&rsquo;s CSAF file uses <code>optional_component_of</code> for a component, Trivy will not apply that status through the relationship. That is safe in direction (no false suppression), but it can surprise you if you expect the finding to drop.</p>
<h2 id="common-mistakes">Common mistakes</h2>
<ul>
<li><strong>Matching the component alone.</strong> Covered above. It turns a statement about one product into a statement about all of them.</li>
<li><strong>Trusting <code>known_not_affected</code> with no impact statement.</strong> The profile requires a flag or an impact threat for each such product. If neither exists, the document does not satisfy the profile; send it back to the vendor rather than suppressing.</li>
<li><strong>Reading only <code>branches</code>.</strong> Products in <code>full_product_names</code> and relationships carry IDs too. A parser that only walks branches will report &ldquo;unknown product&rdquo; for most relationship-heavy files.</li>
<li><strong>Treating <code>recommended</code> as fixed.</strong> The spec allows recommending a version from the affected group.</li>
<li><strong>Ignoring <code>tracking.version</code> and <code>current_release_date</code>.</strong> VEX files are revised as investigations finish. Store the version you applied, and re-apply when it changes.</li>
</ul>
<h2 id="where-this-fits">Where this fits</h2>
<p>VEX is one input to a patch decision, not the decision. In our <a href="/posts/vulnerability-prioritization-workflow-cve-record-to-patch-ticket/">vulnerability prioritization workflow</a>, a supplier VEX statement is the step that can close a ticket before KEV, EPSS or SSVC are weighed. For the SBOM side of the join, the <a href="/posts/sbom-minimum-elements-2026-what-cisa-and-partners-changed-from-the-2021-ntia-baseline/">SBOM minimum elements guide</a> covers which identifiers your SBOM should carry in the first place. Without purls in the SBOM, none of this matching works.</p>
<h2 id="limits-of-this-article">Limits of this article</h2>
<p>We read CSAF 2.0 from the OASIS TC&rsquo;s GitHub repository (the editor&rsquo;s draft prose, headed &ldquo;OASIS Standard, 18 November 2022&rdquo;, and the JSON schema) rather than the copy hosted on docs.oasis-open.org. CSAF 2.1 is still a draft in that repository and may change field names or add statuses. We did not download a Red Hat VEX file; Red Hat&rsquo;s structure is described from its own announcements. The purl matching rules are a community convention, not part of the purl standard. Our test document is synthetic.</p>
<h2 id="sources-and-verification">Sources and verification</h2>
<table>
  <thead>
      <tr>
          <th>Important claim</th>
          <th>Source</th>
          <th>Status</th>
      </tr>
  </thead>
  <tbody>
      <tr>
          <td>CSAF 2.0 is an OASIS Standard dated 18 November 2022; VEX profile requirements (section 4.5)</td>
          <td><a href="https://github.com/oasis-tcs/csaf/blob/master/csaf_2.0/prose/csaf-v2-editor-draft.md">CSAF 2.0 prose, OASIS TC repository</a></td>
          <td>Qualified (TC repository copy)</td>
      </tr>
      <tr>
          <td>Eight product_status lists and their definitions; flag labels; remediation categories; relationship categories</td>
          <td>Same document, sections 3.2.3.9, 3.2.3.5, 3.2.3.12.1, 3.2.2.4</td>
          <td>Verified</td>
      </tr>
      <tr>
          <td>Contradiction groups must be pairwise disjoint; recommended may come from any group</td>
          <td>Same document, section 6.1.6</td>
          <td>Verified</td>
      </tr>
      <tr>
          <td>purl helper pattern and &ldquo;does not completely evaluate&rdquo; note</td>
          <td>Same document, section 3.1.3.3.4</td>
          <td>Verified</td>
      </tr>
      <tr>
          <td>Example document is schema-valid</td>
          <td><a href="https://github.com/oasis-tcs/csaf/blob/master/csaf_2.0/json_schema/csaf_json_schema.json">CSAF 2.0 JSON schema</a>, validated with Python jsonschema</td>
          <td>Verified (our test)</td>
      </tr>
      <tr>
          <td>Red Hat VEX files: per CVE, product_tree with relationships, purls extended to unfixed rpm/oci/rpmmod components at GA</td>
          <td><a href="https://www.redhat.com/en/blog/red-hat-vex-files-cves-are-now-generally-available">Red Hat blog, 10 July 2024</a>; <a href="https://www.redhat.com/en/blog/vulnerability-exploitability-exchange-vex-beta-files-now-available">beta announcement, 16 October 2023</a></td>
          <td>Qualified (vendor announcement; GA post read via a localized copy)</td>
      </tr>
      <tr>
          <td>Trivy CSAF matcher uses known_not_affected and fixed; three relationship categories</td>
          <td><a href="https://github.com/aquasecurity/trivy/blob/v0.76.1/pkg/vex/csaf.go">Trivy v0.76.1 pkg/vex/csaf.go</a></td>
          <td>Verified</td>
      </tr>
      <tr>
          <td>Trivy CSAF targets, relationship handling and purl matching rules</td>
          <td><a href="https://github.com/aquasecurity/trivy/blob/v0.76.1/docs/guide/supply-chain/vex/file.md">Trivy v0.76.1 VEX file documentation</a></td>
          <td>Verified</td>
      </tr>
  </tbody>
</table>
]]></content:encoded></item><item><title>CycloneDX VEX: analysis.state and justification to OpenVEX</title><link>https://firewallsync.com/posts/cyclonedx-vex-analysis-state-justification-openvex-csaf-mapping/</link><guid>https://firewallsync.com/posts/cyclonedx-vex-analysis-state-justification-openvex-csaf-mapping/</guid><pubDate>Tue, 03 Nov 2026 04:40:00 +0000</pubDate><dc:creator>Craig Leslie</dc:creator><category>AppSec &amp; APIs</category><description>CycloneDX VEX uses six analysis states and nine justifications; OpenVEX and CSAF use four statuses and five justifications. Here is a field-by-field mapping, which pairs line up and which do not, how Trivy reads CycloneDX VEX, and a tested Python converter that refuses to invent justifications.</description><enclosure url="https://firewallsync.com/posts/cyclonedx-vex-analysis-state-justification-openvex-csaf-mapping/cover_hu15575583779999317849.jpg" type="image/jpeg" length="0"/><media:content url="https://firewallsync.com/posts/cyclonedx-vex-analysis-state-justification-openvex-csaf-mapping/cover_hu15575583779999317849.jpg" medium="image" type="image/jpeg" width="1200" height="630"/><content:encoded><![CDATA[<p><img src="https://firewallsync.com/posts/cyclonedx-vex-analysis-state-justification-openvex-csaf-mapping/cover_hu15575583779999317849.jpg" alt="Close-up of a silver modular synthesizer panel with black knobs, patched with pink, green, orange, red and yellow cables" width="1200" height="630"></p><p><strong>Scope.</strong> This is a field-level mapping guide. We compared the CycloneDX JSON schemas for 1.6 and 1.7 (identical enums for the fields below), OpenVEX specification v0.2.0 and its JSON schema, and the CSAF 2.0 JSON schema and VEX profile text from the OASIS TC repository, then read how Trivy (main branch, commit <code>1d1ab074</code>, November 2, 2026) consumes CycloneDX VEX. The converter below was run with Python 3.13; its output validated against the OpenVEX 0.2.0 JSON schema and its inputs against the CycloneDX 1.6 schema. Our <a href="/posts/vex-explained-what-a-not-affected-statement-means-and-how-to-read-one/">VEX explainer</a> covers what the statuses mean and how far to trust them; this article is only about moving statements between formats.</p>
<h2 id="the-short-answer">The short answer</h2>
<p>If you receive CycloneDX VEX and your pipeline speaks OpenVEX or CSAF (or the reverse), the states map almost one-to-one, but the justifications do not.</p>
<table>
  <thead>
      <tr>
          <th>CycloneDX <code>analysis.state</code></th>
          <th>OpenVEX <code>status</code></th>
          <th>CSAF <code>product_status</code></th>
          <th>Trivy (code)</th>
      </tr>
  </thead>
  <tbody>
      <tr>
          <td><code>not_affected</code></td>
          <td><code>not_affected</code></td>
          <td><code>known_not_affected</code></td>
          <td>not_affected</td>
      </tr>
      <tr>
          <td><code>false_positive</code></td>
          <td><code>not_affected</code> (no exact match)</td>
          <td><code>known_not_affected</code> (no exact match)</td>
          <td>not_affected</td>
      </tr>
      <tr>
          <td><code>exploitable</code></td>
          <td><code>affected</code></td>
          <td><code>known_affected</code></td>
          <td>affected</td>
      </tr>
      <tr>
          <td><code>in_triage</code></td>
          <td><code>under_investigation</code></td>
          <td><code>under_investigation</code></td>
          <td>under_investigation</td>
      </tr>
      <tr>
          <td><code>resolved</code></td>
          <td><code>fixed</code></td>
          <td><code>fixed</code></td>
          <td>fixed</td>
      </tr>
      <tr>
          <td><code>resolved_with_pedigree</code></td>
          <td><code>fixed</code> (pedigree evidence is lost)</td>
          <td><code>fixed</code></td>
          <td>fixed</td>
      </tr>
  </tbody>
</table>
<p>Of CycloneDX&rsquo;s nine justifications, only <code>code_not_present</code> and <code>code_not_reachable</code> have a clear counterpart among the five CISA-derived labels that OpenVEX and CSAF share. Convert those two; carry the other seven as text.</p>
<h2 id="where-vex-sits-in-a-cyclonedx-document">Where VEX sits in a CycloneDX document</h2>
<p>CycloneDX has no separate VEX document type. VEX is the <code>vulnerabilities</code> array of a BOM, and the fields that matter are:</p>
<ul>
<li><code>id</code>: the vulnerability identifier, such as a CVE ID.</li>
<li><code>affects[].ref</code>: what the statement is about. The schema allows a <code>bom-ref</code> in the same document or a BOM-Link element. A BOM-Link has the form <code>urn:cdx:serialNumber/version#bom-ref</code>, and the schema&rsquo;s pattern requires the serial number UUID, a version of 1 or more, and a fragment.</li>
<li><code>analysis.state</code>: one of <code>resolved</code>, <code>resolved_with_pedigree</code>, <code>exploitable</code>, <code>in_triage</code>, <code>false_positive</code>, <code>not_affected</code>.</li>
<li><code>analysis.justification</code>: one of nine reasons, described below.</li>
<li><code>analysis.response</code>: zero or more of <code>can_not_fix</code>, <code>will_not_fix</code>, <code>update</code>, <code>rollback</code>, <code>workaround_available</code>.</li>
<li><code>analysis.detail</code>: free text. The schema says that if a vulnerability is not exploitable, &ldquo;this field should include specific details on why the component or service is not impacted.&rdquo;</li>
</ul>
<p>A VEX statement can sit inside the SBOM itself or in a separate BOM that only has <code>vulnerabilities</code> and refers back to the SBOM by BOM-Link. That second pattern matters for tooling, below.</p>
<h2 id="states-four-clean-pairs-and-two-lossy-ones">States: four clean pairs and two lossy ones</h2>
<p>The CycloneDX schema defines the six states in its <code>meta:enum</code>. Four map directly:</p>
<ul>
<li><code>not_affected</code>: &ldquo;The component or service is not affected by the vulnerability. Justification should be specified for all not_affected cases.&rdquo; This is OpenVEX <code>not_affected</code> and CSAF <code>known_not_affected</code>.</li>
<li><code>exploitable</code>: &ldquo;The vulnerability may be directly or indirectly exploitable.&rdquo; This is OpenVEX <code>affected</code> and CSAF <code>known_affected</code>.</li>
<li><code>in_triage</code>: &ldquo;The vulnerability is being investigated.&rdquo; This is <code>under_investigation</code> in both.</li>
<li><code>resolved</code>: &ldquo;The vulnerability has been remediated.&rdquo; This is <code>fixed</code> in both.</li>
</ul>
<p>Two lose meaning:</p>
<ul>
<li><strong><code>false_positive</code></strong>: &ldquo;The vulnerability is not specific to the component or service and was falsely identified or associated.&rdquo; OpenVEX and CSAF have no status for &ldquo;the scanner was wrong&rdquo;. The safe target is <code>not_affected</code>, which is also what Trivy&rsquo;s <code>cdxStatus</code> function does (<code>case cdx.IASFalsePositive, cdx.IASNotAffected: return types.FindingStatusNotAffected</code>). Keep the word <code>false_positive</code> in the impact statement so a reviewer can see it.</li>
<li><strong><code>resolved_with_pedigree</code></strong>: remediated &ldquo;and evidence of the changes are provided in the affected components pedigree&rdquo;. It becomes <code>fixed</code>, and the pointer to pedigree evidence is lost unless you keep it as text.</li>
</ul>
<h2 id="justifications-two-of-nine-line-up">Justifications: two of nine line up</h2>
<p>OpenVEX&rsquo;s five justification labels come from CISA&rsquo;s June 2022 status-justification document, and the CSAF 2.0 schema&rsquo;s <code>flags[].label</code> uses the same five strings. CycloneDX defines a different set of nine. Here is each one with its CycloneDX definition and our reading of the closest OpenVEX/CSAF label.</p>
<table>
  <thead>
      <tr>
          <th>CycloneDX <code>justification</code></th>
          <th>CycloneDX definition</th>
          <th>OpenVEX / CSAF label</th>
          <th>Our call</th>
      </tr>
  </thead>
  <tbody>
      <tr>
          <td><code>code_not_present</code></td>
          <td>&ldquo;The code has been removed or tree-shaked.&rdquo;</td>
          <td><code>vulnerable_code_not_present</code></td>
          <td>Map</td>
      </tr>
      <tr>
          <td><code>code_not_reachable</code></td>
          <td>&ldquo;The vulnerable code is not invoked at runtime.&rdquo;</td>
          <td><code>vulnerable_code_not_in_execute_path</code></td>
          <td>Map</td>
      </tr>
      <tr>
          <td><code>requires_dependency</code></td>
          <td>&ldquo;Exploitability requires a dependency that is not present.&rdquo;</td>
          <td>none exact (<code>component_not_present</code> means the vulnerable component itself is absent)</td>
          <td>Text</td>
      </tr>
      <tr>
          <td><code>requires_configuration</code></td>
          <td>&ldquo;Exploitability requires a configurable option to be set/unset.&rdquo;</td>
          <td>none</td>
          <td>Text</td>
      </tr>
      <tr>
          <td><code>requires_environment</code></td>
          <td>&ldquo;Exploitability requires a certain environment which is not present.&rdquo;</td>
          <td>none</td>
          <td>Text</td>
      </tr>
      <tr>
          <td><code>protected_by_compiler</code></td>
          <td>&ldquo;Exploitability requires a compiler flag to be set/unset.&rdquo;</td>
          <td>none exact</td>
          <td>Text</td>
      </tr>
      <tr>
          <td><code>protected_at_runtime</code></td>
          <td>&ldquo;Exploits are prevented at runtime.&rdquo;</td>
          <td><code>inline_mitigations_already_exist</code> only if the protection cannot be disabled</td>
          <td>Text</td>
      </tr>
      <tr>
          <td><code>protected_at_perimeter</code></td>
          <td>&ldquo;Attacks are blocked at physical, logical, or network perimeter.&rdquo;</td>
          <td>none</td>
          <td>Text</td>
      </tr>
      <tr>
          <td><code>protected_by_mitigating_control</code></td>
          <td>&ldquo;Preventative measures have been implemented that reduce the likelihood and/or impact of the vulnerability.&rdquo;</td>
          <td>none</td>
          <td>Text</td>
      </tr>
  </tbody>
</table>
<p>Why so strict? The OpenVEX spec defines <code>inline_mitigations_already_exist</code> as built-in protections that &ldquo;cannot be subverted by the attacker and cannot be configured or disabled by the user.&rdquo; A CycloneDX <code>protected_at_runtime</code> or <code>protected_by_compiler</code> claim does not tell you that. <code>protected_at_perimeter</code> and <code>protected_by_mitigating_control</code> describe the deployment, not the product, and a mitigating control that &ldquo;reduce[s] the likelihood and/or impact&rdquo; is weaker than &ldquo;not affected&rdquo; in the CISA sense.</p>
<p>This mapping is our editorial reading of the published definitions. We did not find a mapping table published by the CycloneDX project or CISA.</p>
<p>OpenVEX gives you a way out: for <code>not_affected</code>, &ldquo;a VEX statement MUST include either a status justification or an impact_statement.&rdquo; So you can emit a <code>not_affected</code> statement with no label and an impact statement that preserves the original CycloneDX reason. CSAF&rsquo;s VEX profile has the same escape hatch: each <code>known_not_affected</code> product needs either a machine-readable flag or a human-readable justification in <code>threats</code> with category <code>impact</code>.</p>
<h2 id="responses-and-action-statements">Responses and action statements</h2>
<p>For affected products, both targets require an action:</p>
<ul>
<li>OpenVEX: for <code>affected</code>, &ldquo;a VEX statement MUST include a statement that SHOULD describe actions to remediate or mitigate the vulnerability&rdquo; (<code>action_statement</code>).</li>
<li>CSAF VEX profile: for <code>known_affected</code>, &ldquo;additional product specific information SHALL be provided in <code>/vulnerabilities[]/remediations</code> as an action statement.&rdquo;</li>
</ul>
<p>CycloneDX&rsquo;s <code>response</code> values give you a starting point. <code>update</code> and <code>rollback</code> fit CSAF&rsquo;s <code>vendor_fix</code> remediation category, <code>workaround_available</code> fits <code>workaround</code>, and <code>will_not_fix</code> / <code>can_not_fix</code> fit <code>no_fix_planned</code> (or <code>none_available</code>), which the CSAF profile explicitly permits for an action statement. OpenVEX takes a free-text <code>action_statement</code>, so join the responses with <code>analysis.detail</code>. If an <code>exploitable</code> statement has neither a response nor detail, the converted statement will be valid but useless; send it back to the supplier.</p>
<h2 id="bom-link-the-part-that-silently-drops-statements">BOM-Link: the part that silently drops statements</h2>
<p>A CycloneDX VEX BOM that references components by BOM-Link is bound to one SBOM version. Trivy&rsquo;s docs (v0.67) say the tool &ldquo;only supports the Independent BOM and VEX BOM format, so you need to provide a separate VEX file alongside the SBOM,&rdquo; that &ldquo;BOM-Links must be placed in <code>affects.ref</code>,&rdquo; and that the input SBOM must be CycloneDX. The usage example is <code>trivy sbom trivy.sbom.cdx --vex trivy.vex.cdx</code>. The feature is marked experimental.</p>
<p>Trivy&rsquo;s code adds a detail the docs do not spell out: if the BOM-Link&rsquo;s serial number or version does not equal the scanned SBOM&rsquo;s, it logs <code>URN doesn't match with SBOM</code> and skips the statement. Regenerate the SBOM (new serial number or version) without regenerating the VEX, and every suppression stops applying. That fails safe, since findings come back rather than disappear, but it surprises teams.</p>
<p>OpenVEX has no BOM-Link. Products are identified by an <code>@id</code> such as a Package URL, so a converter has to resolve each BOM-Link to the referenced component&rsquo;s <code>purl</code> in the SBOM. That is why the converter below takes both files.</p>
<h2 id="a-tested-converter-cyclonedx-vex-to-openvex">A tested converter: CycloneDX VEX to OpenVEX</h2>
<p>This Python 3 script reads a CycloneDX SBOM and a separate CycloneDX VEX BOM and writes an OpenVEX 0.2.0 document. It maps states as in the first table, maps only the two clean justifications, and keeps everything else as text. It is illustrative, not production-ready: it does not handle version ranges in <code>affects[].versions</code>, services, or nested BOMs beyond <code>components</code>.</p>
<div class="highlight"><pre tabindex="0" style="color:#f8f8f2;background-color:#272822;-moz-tab-size:4;-o-tab-size:4;tab-size:4;"><code class="language-python" data-lang="python"><span style="display:flex;"><span><span style="color:#75715e">#!/usr/bin/env python3</span>
</span></span><span style="display:flex;"><span><span style="color:#e6db74">&#34;&#34;&#34;Convert a CycloneDX VEX BOM (independent VEX, BOM-Link refs) to OpenVEX v0.2.0.
</span></span></span><span style="display:flex;"><span><span style="color:#e6db74">Usage: python3 cdx2openvex.py sbom.cdx.json vex.cdx.json author &gt; out.openvex.json&#34;&#34;&#34;</span>
</span></span><span style="display:flex;"><span><span style="color:#f92672">import</span> json<span style="color:#f92672">,</span> sys<span style="color:#f92672">,</span> hashlib
</span></span><span style="display:flex;"><span><span style="color:#f92672">from</span> datetime <span style="color:#f92672">import</span> datetime, timezone
</span></span><span style="display:flex;"><span>
</span></span><span style="display:flex;"><span>STATUS <span style="color:#f92672">=</span> {  <span style="color:#75715e"># CycloneDX analysis.state -&gt; OpenVEX status</span>
</span></span><span style="display:flex;"><span>    <span style="color:#e6db74">&#34;not_affected&#34;</span>: <span style="color:#e6db74">&#34;not_affected&#34;</span>, <span style="color:#e6db74">&#34;false_positive&#34;</span>: <span style="color:#e6db74">&#34;not_affected&#34;</span>,
</span></span><span style="display:flex;"><span>    <span style="color:#e6db74">&#34;exploitable&#34;</span>: <span style="color:#e6db74">&#34;affected&#34;</span>, <span style="color:#e6db74">&#34;in_triage&#34;</span>: <span style="color:#e6db74">&#34;under_investigation&#34;</span>,
</span></span><span style="display:flex;"><span>    <span style="color:#e6db74">&#34;resolved&#34;</span>: <span style="color:#e6db74">&#34;fixed&#34;</span>, <span style="color:#e6db74">&#34;resolved_with_pedigree&#34;</span>: <span style="color:#e6db74">&#34;fixed&#34;</span>,
</span></span><span style="display:flex;"><span>}
</span></span><span style="display:flex;"><span><span style="color:#75715e"># Only the pairs whose definitions line up; everything else is carried as text.</span>
</span></span><span style="display:flex;"><span>JUSTIFICATION <span style="color:#f92672">=</span> {
</span></span><span style="display:flex;"><span>    <span style="color:#e6db74">&#34;code_not_present&#34;</span>: <span style="color:#e6db74">&#34;vulnerable_code_not_present&#34;</span>,
</span></span><span style="display:flex;"><span>    <span style="color:#e6db74">&#34;code_not_reachable&#34;</span>: <span style="color:#e6db74">&#34;vulnerable_code_not_in_execute_path&#34;</span>,
</span></span><span style="display:flex;"><span>}
</span></span><span style="display:flex;"><span>
</span></span><span style="display:flex;"><span><span style="color:#66d9ef">def</span> <span style="color:#a6e22e">purls_by_ref</span>(sbom):
</span></span><span style="display:flex;"><span>    serial, version <span style="color:#f92672">=</span> sbom[<span style="color:#e6db74">&#34;serialNumber&#34;</span>], sbom<span style="color:#f92672">.</span>get(<span style="color:#e6db74">&#34;version&#34;</span>, <span style="color:#ae81ff">1</span>)
</span></span><span style="display:flex;"><span>    out, stack <span style="color:#f92672">=</span> {}, list(sbom<span style="color:#f92672">.</span>get(<span style="color:#e6db74">&#34;components&#34;</span>, []))
</span></span><span style="display:flex;"><span>    <span style="color:#66d9ef">while</span> stack:
</span></span><span style="display:flex;"><span>        c <span style="color:#f92672">=</span> stack<span style="color:#f92672">.</span>pop()
</span></span><span style="display:flex;"><span>        <span style="color:#66d9ef">if</span> <span style="color:#e6db74">&#34;bom-ref&#34;</span> <span style="color:#f92672">in</span> c <span style="color:#f92672">and</span> <span style="color:#e6db74">&#34;purl&#34;</span> <span style="color:#f92672">in</span> c:
</span></span><span style="display:flex;"><span>            out[<span style="color:#e6db74">f</span><span style="color:#e6db74">&#34;urn:cdx:</span><span style="color:#e6db74">{</span>serial<span style="color:#f92672">.</span>removeprefix(<span style="color:#e6db74">&#39;urn:uuid:&#39;</span>)<span style="color:#e6db74">}</span><span style="color:#e6db74">/</span><span style="color:#e6db74">{</span>version<span style="color:#e6db74">}</span><span style="color:#e6db74">#</span><span style="color:#e6db74">{</span>c[<span style="color:#e6db74">&#39;bom-ref&#39;</span>]<span style="color:#e6db74">}</span><span style="color:#e6db74">&#34;</span>] <span style="color:#f92672">=</span> c[<span style="color:#e6db74">&#34;purl&#34;</span>]
</span></span><span style="display:flex;"><span>        stack<span style="color:#f92672">.</span>extend(c<span style="color:#f92672">.</span>get(<span style="color:#e6db74">&#34;components&#34;</span>, []))
</span></span><span style="display:flex;"><span>    <span style="color:#66d9ef">return</span> out
</span></span><span style="display:flex;"><span>
</span></span><span style="display:flex;"><span><span style="color:#66d9ef">def</span> <span style="color:#a6e22e">convert</span>(sbom, vex, author):
</span></span><span style="display:flex;"><span>    refs, statements, problems <span style="color:#f92672">=</span> purls_by_ref(sbom), [], []
</span></span><span style="display:flex;"><span>    <span style="color:#66d9ef">for</span> v <span style="color:#f92672">in</span> vex<span style="color:#f92672">.</span>get(<span style="color:#e6db74">&#34;vulnerabilities&#34;</span>, []):
</span></span><span style="display:flex;"><span>        a <span style="color:#f92672">=</span> v<span style="color:#f92672">.</span>get(<span style="color:#e6db74">&#34;analysis&#34;</span>, {})
</span></span><span style="display:flex;"><span>        state <span style="color:#f92672">=</span> a<span style="color:#f92672">.</span>get(<span style="color:#e6db74">&#34;state&#34;</span>)
</span></span><span style="display:flex;"><span>        <span style="color:#66d9ef">if</span> state <span style="color:#f92672">not</span> <span style="color:#f92672">in</span> STATUS:
</span></span><span style="display:flex;"><span>            problems<span style="color:#f92672">.</span>append(<span style="color:#e6db74">f</span><span style="color:#e6db74">&#34;</span><span style="color:#e6db74">{</span>v[<span style="color:#e6db74">&#39;id&#39;</span>]<span style="color:#e6db74">}</span><span style="color:#e6db74">: no analysis.state, skipped&#34;</span>); <span style="color:#66d9ef">continue</span>
</span></span><span style="display:flex;"><span>        products <span style="color:#f92672">=</span> []
</span></span><span style="display:flex;"><span>        <span style="color:#66d9ef">for</span> af <span style="color:#f92672">in</span> v<span style="color:#f92672">.</span>get(<span style="color:#e6db74">&#34;affects&#34;</span>, []):
</span></span><span style="display:flex;"><span>            purl <span style="color:#f92672">=</span> refs<span style="color:#f92672">.</span>get(af[<span style="color:#e6db74">&#34;ref&#34;</span>])
</span></span><span style="display:flex;"><span>            <span style="color:#66d9ef">if</span> purl: products<span style="color:#f92672">.</span>append({<span style="color:#e6db74">&#34;@id&#34;</span>: purl})
</span></span><span style="display:flex;"><span>            <span style="color:#66d9ef">else</span>: problems<span style="color:#f92672">.</span>append(<span style="color:#e6db74">f</span><span style="color:#e6db74">&#34;</span><span style="color:#e6db74">{</span>v[<span style="color:#e6db74">&#39;id&#39;</span>]<span style="color:#e6db74">}</span><span style="color:#e6db74">: </span><span style="color:#e6db74">{</span>af[<span style="color:#e6db74">&#39;ref&#39;</span>]<span style="color:#e6db74">}</span><span style="color:#e6db74"> not found in SBOM&#34;</span>)
</span></span><span style="display:flex;"><span>        <span style="color:#66d9ef">if</span> <span style="color:#f92672">not</span> products: <span style="color:#66d9ef">continue</span>
</span></span><span style="display:flex;"><span>        s <span style="color:#f92672">=</span> {<span style="color:#e6db74">&#34;vulnerability&#34;</span>: {<span style="color:#e6db74">&#34;name&#34;</span>: v[<span style="color:#e6db74">&#34;id&#34;</span>]}, <span style="color:#e6db74">&#34;products&#34;</span>: products, <span style="color:#e6db74">&#34;status&#34;</span>: STATUS[state]}
</span></span><span style="display:flex;"><span>        detail <span style="color:#f92672">=</span> a<span style="color:#f92672">.</span>get(<span style="color:#e6db74">&#34;detail&#34;</span>, <span style="color:#e6db74">&#34;&#34;</span>)<span style="color:#f92672">.</span>strip()
</span></span><span style="display:flex;"><span>        <span style="color:#66d9ef">if</span> s[<span style="color:#e6db74">&#34;status&#34;</span>] <span style="color:#f92672">==</span> <span style="color:#e6db74">&#34;not_affected&#34;</span>:
</span></span><span style="display:flex;"><span>            j <span style="color:#f92672">=</span> JUSTIFICATION<span style="color:#f92672">.</span>get(a<span style="color:#f92672">.</span>get(<span style="color:#e6db74">&#34;justification&#34;</span>))
</span></span><span style="display:flex;"><span>            <span style="color:#66d9ef">if</span> j: s[<span style="color:#e6db74">&#34;justification&#34;</span>] <span style="color:#f92672">=</span> j
</span></span><span style="display:flex;"><span>            note <span style="color:#f92672">=</span> <span style="color:#e6db74">f</span><span style="color:#e6db74">&#34;CycloneDX state=</span><span style="color:#e6db74">{</span>state<span style="color:#e6db74">}</span><span style="color:#e6db74">, justification=</span><span style="color:#e6db74">{</span>a<span style="color:#f92672">.</span>get(<span style="color:#e6db74">&#39;justification&#39;</span>, <span style="color:#e6db74">&#39;none&#39;</span>)<span style="color:#e6db74">}</span><span style="color:#e6db74">&#34;</span>
</span></span><span style="display:flex;"><span>            s[<span style="color:#e6db74">&#34;impact_statement&#34;</span>] <span style="color:#f92672">=</span> <span style="color:#e6db74">f</span><span style="color:#e6db74">&#34;</span><span style="color:#e6db74">{</span>note<span style="color:#e6db74">}</span><span style="color:#e6db74">. </span><span style="color:#e6db74">{</span>detail<span style="color:#e6db74">}</span><span style="color:#e6db74">&#34;</span><span style="color:#f92672">.</span>strip()
</span></span><span style="display:flex;"><span>        <span style="color:#66d9ef">elif</span> s[<span style="color:#e6db74">&#34;status&#34;</span>] <span style="color:#f92672">==</span> <span style="color:#e6db74">&#34;affected&#34;</span>:
</span></span><span style="display:flex;"><span>            resp <span style="color:#f92672">=</span> <span style="color:#e6db74">&#34;, &#34;</span><span style="color:#f92672">.</span>join(a<span style="color:#f92672">.</span>get(<span style="color:#e6db74">&#34;response&#34;</span>, [])) <span style="color:#f92672">or</span> <span style="color:#e6db74">&#34;none given&#34;</span>
</span></span><span style="display:flex;"><span>            s[<span style="color:#e6db74">&#34;action_statement&#34;</span>] <span style="color:#f92672">=</span> <span style="color:#e6db74">f</span><span style="color:#e6db74">&#34;CycloneDX response: </span><span style="color:#e6db74">{</span>resp<span style="color:#e6db74">}</span><span style="color:#e6db74">. </span><span style="color:#e6db74">{</span>detail<span style="color:#e6db74">}</span><span style="color:#e6db74">&#34;</span><span style="color:#f92672">.</span>strip()
</span></span><span style="display:flex;"><span>        statements<span style="color:#f92672">.</span>append(s)
</span></span><span style="display:flex;"><span>    body <span style="color:#f92672">=</span> json<span style="color:#f92672">.</span>dumps(statements, sort_keys<span style="color:#f92672">=</span><span style="color:#66d9ef">True</span>)<span style="color:#f92672">.</span>encode()
</span></span><span style="display:flex;"><span>    doc <span style="color:#f92672">=</span> {<span style="color:#e6db74">&#34;@context&#34;</span>: <span style="color:#e6db74">&#34;https://openvex.dev/ns/v0.2.0&#34;</span>,
</span></span><span style="display:flex;"><span>           <span style="color:#e6db74">&#34;@id&#34;</span>: <span style="color:#e6db74">&#34;https://example.com/vex/&#34;</span> <span style="color:#f92672">+</span> hashlib<span style="color:#f92672">.</span>sha256(body)<span style="color:#f92672">.</span>hexdigest()[:<span style="color:#ae81ff">16</span>],
</span></span><span style="display:flex;"><span>           <span style="color:#e6db74">&#34;author&#34;</span>: author,
</span></span><span style="display:flex;"><span>           <span style="color:#e6db74">&#34;timestamp&#34;</span>: datetime<span style="color:#f92672">.</span>now(timezone<span style="color:#f92672">.</span>utc)<span style="color:#f92672">.</span>isoformat(timespec<span style="color:#f92672">=</span><span style="color:#e6db74">&#34;seconds&#34;</span>),
</span></span><span style="display:flex;"><span>           <span style="color:#e6db74">&#34;version&#34;</span>: <span style="color:#ae81ff">1</span>, <span style="color:#e6db74">&#34;statements&#34;</span>: statements}
</span></span><span style="display:flex;"><span>    <span style="color:#66d9ef">return</span> doc, problems
</span></span><span style="display:flex;"><span>
</span></span><span style="display:flex;"><span><span style="color:#66d9ef">if</span> __name__ <span style="color:#f92672">==</span> <span style="color:#e6db74">&#34;__main__&#34;</span>:
</span></span><span style="display:flex;"><span>    sbom, vex <span style="color:#f92672">=</span> (json<span style="color:#f92672">.</span>load(open(p)) <span style="color:#66d9ef">for</span> p <span style="color:#f92672">in</span> sys<span style="color:#f92672">.</span>argv[<span style="color:#ae81ff">1</span>:<span style="color:#ae81ff">3</span>])
</span></span><span style="display:flex;"><span>    doc, problems <span style="color:#f92672">=</span> convert(sbom, vex, sys<span style="color:#f92672">.</span>argv[<span style="color:#ae81ff">3</span>])
</span></span><span style="display:flex;"><span>    json<span style="color:#f92672">.</span>dump(doc, sys<span style="color:#f92672">.</span>stdout, indent<span style="color:#f92672">=</span><span style="color:#ae81ff">2</span>)
</span></span><span style="display:flex;"><span>    <span style="color:#66d9ef">for</span> p <span style="color:#f92672">in</span> problems: print(<span style="color:#e6db74">&#34;WARN&#34;</span>, p, file<span style="color:#f92672">=</span>sys<span style="color:#f92672">.</span>stderr)
</span></span></code></pre></div><h3 id="test-run">Test run</h3>
<p>We fed it a three-component CycloneDX 1.6 SBOM (log4j-core 2.14.1, jackson-databind 2.13.0, snakeyaml 1.30) and a VEX BOM with four statements. The assessments in the VEX are invented test data, not real vendor findings:</p>
<ol>
<li>CVE-2021-44228 on log4j-core: <code>not_affected</code>, <code>code_not_reachable</code>.</li>
<li>CVE-2022-42003 on jackson-databind: <code>not_affected</code>, <code>requires_configuration</code>.</li>
<li>CVE-2022-1471 on snakeyaml: <code>exploitable</code>, response <code>update</code>.</li>
<li>CVE-2021-44228 again, but with a BOM-Link naming SBOM version <code>2</code> instead of <code>1</code>.</li>
</ol>
<p>Both input files passed <code>check-jsonschema</code> against the CycloneDX 1.6 schema. The run printed one warning to stderr and three statements; the output validated against <code>openvex_json_schema.json</code> (v0.2.0) with the Python <code>jsonschema</code> package:</p>
<div class="highlight"><pre tabindex="0" style="color:#f8f8f2;background-color:#272822;-moz-tab-size:4;-o-tab-size:4;tab-size:4;"><code class="language-text" data-lang="text"><span style="display:flex;"><span>WARN CVE-2021-44228: urn:cdx:3e671687-395b-41f5-a30f-a58921a69b79/2#pkg-log4j not found in SBOM
</span></span></code></pre></div><p>The <code>statements</code> array of the output:</p>
<div class="highlight"><pre tabindex="0" style="color:#f8f8f2;background-color:#272822;-moz-tab-size:4;-o-tab-size:4;tab-size:4;"><code class="language-json" data-lang="json"><span style="display:flex;"><span>[
</span></span><span style="display:flex;"><span>{
</span></span><span style="display:flex;"><span>  <span style="color:#f92672">&#34;vulnerability&#34;</span>: { <span style="color:#f92672">&#34;name&#34;</span>: <span style="color:#e6db74">&#34;CVE-2021-44228&#34;</span> },
</span></span><span style="display:flex;"><span>  <span style="color:#f92672">&#34;products&#34;</span>: [ { <span style="color:#f92672">&#34;@id&#34;</span>: <span style="color:#e6db74">&#34;pkg:maven/org.apache.logging.log4j/log4j-core@2.14.1&#34;</span> } ],
</span></span><span style="display:flex;"><span>  <span style="color:#f92672">&#34;status&#34;</span>: <span style="color:#e6db74">&#34;not_affected&#34;</span>,
</span></span><span style="display:flex;"><span>  <span style="color:#f92672">&#34;justification&#34;</span>: <span style="color:#e6db74">&#34;vulnerable_code_not_in_execute_path&#34;</span>,
</span></span><span style="display:flex;"><span>  <span style="color:#f92672">&#34;impact_statement&#34;</span>: <span style="color:#e6db74">&#34;CycloneDX state=not_affected, justification=code_not_reachable. JNDI lookups are never invoked; the app logs through SLF4J with Logback.&#34;</span>
</span></span><span style="display:flex;"><span>},
</span></span><span style="display:flex;"><span>{
</span></span><span style="display:flex;"><span>  <span style="color:#f92672">&#34;vulnerability&#34;</span>: { <span style="color:#f92672">&#34;name&#34;</span>: <span style="color:#e6db74">&#34;CVE-2022-42003&#34;</span> },
</span></span><span style="display:flex;"><span>  <span style="color:#f92672">&#34;products&#34;</span>: [ { <span style="color:#f92672">&#34;@id&#34;</span>: <span style="color:#e6db74">&#34;pkg:maven/com.fasterxml.jackson.core/jackson-databind@2.13.0&#34;</span> } ],
</span></span><span style="display:flex;"><span>  <span style="color:#f92672">&#34;status&#34;</span>: <span style="color:#e6db74">&#34;not_affected&#34;</span>,
</span></span><span style="display:flex;"><span>  <span style="color:#f92672">&#34;impact_statement&#34;</span>: <span style="color:#e6db74">&#34;CycloneDX state=not_affected, justification=requires_configuration. The deserialization feature this issue depends on is disabled in our ObjectMapper configuration.&#34;</span>
</span></span><span style="display:flex;"><span>},
</span></span><span style="display:flex;"><span>{
</span></span><span style="display:flex;"><span>  <span style="color:#f92672">&#34;vulnerability&#34;</span>: { <span style="color:#f92672">&#34;name&#34;</span>: <span style="color:#e6db74">&#34;CVE-2022-1471&#34;</span> },
</span></span><span style="display:flex;"><span>  <span style="color:#f92672">&#34;products&#34;</span>: [ { <span style="color:#f92672">&#34;@id&#34;</span>: <span style="color:#e6db74">&#34;pkg:maven/org.yaml/snakeyaml@1.30&#34;</span> } ],
</span></span><span style="display:flex;"><span>  <span style="color:#f92672">&#34;status&#34;</span>: <span style="color:#e6db74">&#34;affected&#34;</span>,
</span></span><span style="display:flex;"><span>  <span style="color:#f92672">&#34;action_statement&#34;</span>: <span style="color:#e6db74">&#34;CycloneDX response: update. Dependency upgrade ships in release 4.2.&#34;</span>
</span></span><span style="display:flex;"><span>}
</span></span><span style="display:flex;"><span>]
</span></span></code></pre></div><p>The second statement is the important one: it stays <code>not_affected</code> with no invented label, and the reason survives as text. The fourth input statement was dropped with a warning instead of being applied to the wrong SBOM.</p>
<h2 id="common-mistakes">Common mistakes</h2>
<ul>
<li><strong>Mapping every <code>protected_*</code> justification to <code>inline_mitigations_already_exist</code>.</strong> That label claims the protection cannot be disabled. A WAF rule or a compiler flag can.</li>
<li><strong>Dropping <code>false_positive</code> statements</strong> because the target format has no matching status. Map them to <code>not_affected</code> and say why.</li>
<li><strong>Dropping the <code>detail</code> text.</strong> It is often the only evidence a reviewer has, and both OpenVEX and CSAF have a place for it.</li>
<li><strong>Reusing a VEX BOM after regenerating the SBOM.</strong> BOM-Links name an exact serial number and version.</li>
<li><strong>Treating converted VEX as first-party.</strong> Keep the original author. OpenVEX <code>author</code> should be the organization that made the assessment, not the converter.</li>
</ul>
<h2 id="where-this-fits">Where this fits</h2>
<p>VEX is the &ldquo;is my product actually affected&rdquo; step in our <a href="/posts/vulnerability-prioritization-workflow-cve-record-to-patch-ticket/">vulnerability prioritization workflow</a>, after the CVE record and before KEV, SSVC and EPSS. The SBOM that the VEX points at is covered in our guide to <a href="/posts/sbom-minimum-elements-2026-what-cisa-and-partners-changed-from-the-2021-ntia-baseline/">SBOM minimum elements in 2026</a>. If you want a signal for which <code>exploitable</code> statements to fix first, our <a href="/posts/cvss-vs-epss-vs-kev-which-signal-should-decide-what-you-patch-first/">CVSS vs EPSS vs KEV comparison</a> covers the trade-offs.</p>
<h2 id="limits-of-this-article">Limits of this article</h2>
<p>The justification mapping is our reading of the published definitions; no standards body has published it. We read CSAF 2.0 from the OASIS TC&rsquo;s GitHub repository (schema and editor&rsquo;s draft prose) rather than the OASIS-hosted standard. We read Trivy&rsquo;s main branch, not a tagged release, and its docs for v0.67; behaviour may differ in the version you run. We did not run Trivy itself or test the reverse conversion (OpenVEX or CSAF to CycloneDX), which is harder because CycloneDX <code>affects</code> needs a component reference the OpenVEX product may not resolve to.</p>
<h2 id="sources-and-verification">Sources and verification</h2>
<table>
  <thead>
      <tr>
          <th>Important claim</th>
          <th>Source</th>
          <th>Status</th>
      </tr>
  </thead>
  <tbody>
      <tr>
          <td>CycloneDX states, justifications, responses and their definitions; detail field; BOM-Link pattern</td>
          <td><a href="https://github.com/CycloneDX/specification/tree/master/schema">CycloneDX bom-1.6 / bom-1.7 JSON schemas</a></td>
          <td>Verified</td>
      </tr>
      <tr>
          <td>BOM-Link syntax <code>urn:cdx:serialNumber/version#bom-ref</code></td>
          <td><a href="https://www.cyclonedx.org/capabilities/bomlink/">CycloneDX BOM-Link</a></td>
          <td>Verified</td>
      </tr>
      <tr>
          <td>OpenVEX statuses, five justifications, justification or impact_statement rule, action_statement rule</td>
          <td><a href="https://github.com/openvex/spec/blob/main/OPENVEX-SPEC.md">OpenVEX spec v0.2.0</a></td>
          <td>Verified</td>
      </tr>
      <tr>
          <td>CSAF product_status categories, flag labels, remediation categories</td>
          <td><a href="https://github.com/oasis-tcs/csaf/blob/master/csaf_2.0/json_schema/csaf_json_schema.json">CSAF 2.0 JSON schema</a></td>
          <td>Verified</td>
      </tr>
      <tr>
          <td>CSAF VEX profile requirements for known_not_affected and known_affected</td>
          <td><a href="https://github.com/oasis-tcs/csaf/blob/master/csaf_2.0/prose/csaf-v2-editor-draft.md">CSAF 2.0 prose, section 4.5</a></td>
          <td>Qualified (TC repository draft text)</td>
      </tr>
      <tr>
          <td>Trivy maps false_positive to not_affected and skips BOM-Links that do not match the SBOM</td>
          <td><a href="https://github.com/aquasecurity/trivy/blob/main/pkg/vex/cyclonedx.go">Trivy pkg/vex/cyclonedx.go</a></td>
          <td>Verified (main branch, 2026-11-02)</td>
      </tr>
      <tr>
          <td>Trivy CycloneDX VEX: separate VEX BOM, BOM-Link in affects.ref, CycloneDX SBOM only, experimental</td>
          <td><a href="https://trivy.dev/docs/latest/supply-chain/vex/file">Trivy docs: VEX file</a></td>
          <td>Verified</td>
      </tr>
      <tr>
          <td>Converter output and schema validation</td>
          <td>Our run, Python 3.13, jsonschema, check-jsonschema</td>
          <td>Verified (code)</td>
      </tr>
  </tbody>
</table>
]]></content:encoded></item><item><title>Vulnerability Prioritization Workflow: CVE Record to Ticket</title><link>https://firewallsync.com/posts/vulnerability-prioritization-workflow-cve-record-to-patch-ticket/</link><guid>https://firewallsync.com/posts/vulnerability-prioritization-workflow-cve-record-to-patch-ticket/</guid><pubDate>Mon, 02 Nov 2026 04:30:00 +0000</pubDate><dc:creator>John Marshall</dc:creator><category>Security Operations</category><description>A six-step patch-decision flow that takes a scanner finding from CVE record to ticket: check the record state, confirm you are affected, apply supplier VEX, read KEV and CISA's SSVC values, add EPSS, then let your exposure decide. Includes a tested Python script that writes the ticket fields.</description><enclosure url="https://firewallsync.com/posts/vulnerability-prioritization-workflow-cve-record-to-patch-ticket/cover_hu7197188011340061090.jpg" type="image/jpeg" length="0"/><media:content url="https://firewallsync.com/posts/vulnerability-prioritization-workflow-cve-record-to-patch-ticket/cover_hu7197188011340061090.jpg" medium="image" type="image/jpeg" width="1200" height="630"/><content:encoded><![CDATA[<p><img src="https://firewallsync.com/posts/vulnerability-prioritization-workflow-cve-record-to-patch-ticket/cover_hu7197188011340061090.jpg" alt="View from the side of a passenger train of a railway switch where the tracks split, with a red point indicator, dry golden grassland and brown mountains behind" width="1200" height="630"></p><p><strong>Scope.</strong> This is a workflow guide built on public specifications and feeds, plus one script we ran. On November 2, 2026 we read the CVE JSON schema (5.2.0), CISA&rsquo;s Vulnrichment README, CERT/CC&rsquo;s SSVC deployer documentation and decision table, the OpenVEX specification and the EPSS repository README, and ran the script below against the KEV catalog (version 2026.10.30), the EPSS file scored 2026-11-01 and CVE records from cvelistV5. The assets, exposure ratings and the VEX document in the test are invented for the demonstration. The policy choices in the script are ours, not a standard.</p>
<h2 id="the-workflow-in-one-table">The workflow in one table</h2>
<p>Our comparison of <a href="/posts/cvss-vs-epss-vs-kev-which-signal-should-decide-what-you-patch-first/">CVSS, EPSS and KEV</a> explains what each signal measures. This guide is the plumbing: the order in which a finding from a scanner or SBOM passes through the data, and what lands in the ticket.</p>
<table>
  <thead>
      <tr>
          <th>Step</th>
          <th>Question</th>
          <th>Data you read</th>
          <th>Possible outcome</th>
      </tr>
  </thead>
  <tbody>
      <tr>
          <td>1</td>
          <td>Is the CVE record valid?</td>
          <td><code>cveMetadata.state</code> in the CVE record</td>
          <td>Close if <code>REJECTED</code></td>
      </tr>
      <tr>
          <td>2</td>
          <td>Do we run an affected version?</td>
          <td><code>containers.cna.affected</code>: <code>versions</code>, <code>defaultStatus</code></td>
          <td>Close if unaffected; escalate if unknown</td>
      </tr>
      <tr>
          <td>3</td>
          <td>Has the supplier said we are not affected?</td>
          <td>VEX statement for this product</td>
          <td>Close with the VEX justification</td>
      </tr>
      <tr>
          <td>4</td>
          <td>Is it being exploited?</td>
          <td>KEV entry; CISA ADP SSVC <code>Exploitation</code></td>
          <td>Sets the Exploitation input</td>
      </tr>
      <tr>
          <td>5</td>
          <td>How likely is exploitation?</td>
          <td>EPSS <code>epss</code>, <code>percentile</code></td>
          <td>Re-orders the non-exploited queue</td>
      </tr>
      <tr>
          <td>6</td>
          <td>How exposed and important is this asset?</td>
          <td>Your inventory: System Exposure, Human Impact</td>
          <td>Priority: Defer, Scheduled, Out-of-cycle, Immediate</td>
      </tr>
  </tbody>
</table>
<p>Steps 1 to 3 remove work. Steps 4 to 6 order what remains.</p>
<h2 id="step-1-check-the-record-state">Step 1: check the record state</h2>
<p>A CVE record is either <code>PUBLISHED</code> or <code>REJECTED</code> (the schema&rsquo;s two states), and published records can carry tags such as <code>disputed</code>. A rejected ID has no affected products to evaluate. In our test run, CVE-2026-23915 is a Fortinet-assigned ID that was rejected on January 20, 2026 with the reason &ldquo;Not used&rdquo;, so the finding closes. Our guide to <a href="/posts/cve-record-states-published-rejected-and-disputed-what-each-means-for-vulnerability-triage/">CVE record states</a> covers the tags and edge cases.</p>
<h2 id="step-2-confirm-you-are-affected">Step 2: confirm you are affected</h2>
<p>The CNA&rsquo;s <code>affected</code> block is an algorithm, not a list: walk <code>versions</code>, take the first match, otherwise use <code>defaultStatus</code>, and if that is missing the schema says the status is <code>unknown</code>. Scanner results that only match a product name skip this. Our explainer on <a href="/posts/cve-affected-versions-lessthan-defaultstatus-versiontype/">CVE affected versions</a> shows how <code>lessThan</code>, <code>defaultStatus</code> and <code>versionType</code> combine, with a tested evaluator. Keep three outcomes apart in the ticket: affected, unaffected, and unknown or undetermined. The last needs a person or the vendor advisory.</p>
<h2 id="step-3-apply-supplier-vex">Step 3: apply supplier VEX</h2>
<p>If the vulnerable component ships inside someone else&rsquo;s product, the supplier may publish a VEX (Vulnerability Exploitability eXchange) statement. OpenVEX defines four statuses: <code>not_affected</code> (&ldquo;No remediation is required regarding this vulnerability&rdquo;), <code>affected</code>, <code>fixed</code> and <code>under_investigation</code>. A <code>not_affected</code> statement must carry a justification or an impact statement.</p>
<p>Two cautions. A VEX statement is about a specific product and version, so match on the product identifier, not on the CVE alone; a <code>not_affected</code> statement from an appliance vendor says nothing about your own services that use the same library. And read the justification before closing. Our guide to <a href="/posts/vex-explained-what-a-not-affected-statement-means-and-how-to-read-one/">reading a VEX not-affected statement</a> covers the five justifications and what to question.</p>
<h2 id="step-4-read-the-exploitation-evidence">Step 4: read the exploitation evidence</h2>
<p>Two public sources answer &ldquo;is this being exploited?&rdquo;:</p>
<ul>
<li><strong>KEV.</strong> The <a href="/posts/cisa-kev-json-feed-what-each-field-means-and-how-to-match-it-against-a-scanner-export/">CISA KEV JSON feed</a> lists CVEs with evidence of exploitation, with <code>dateAdded</code>, <code>dueDate</code>, <code>knownRansomwareCampaignUse</code> and, on newer entries, <code>forensicTriage</code>. The catalog we used (version 2026.10.30, released October 30, 2026) had 1,766 entries.</li>
<li><strong>CISA&rsquo;s SSVC values in the CVE record.</strong> CISA&rsquo;s Vulnrichment project writes three SSVC decision points (Exploitation, Automatable, Technical Impact) into a CISA-ADP container. Its README says CISA is &ldquo;assessing new and recent CVEs&rdquo;, and that it will not overwrite the CNA&rsquo;s data. Each value set carries a timestamp. Our <a href="/posts/cisa-vulnrichment-how-to-read-ssvc-values-in-a-cve-record-and-turn-them-into-a-patch-decision/">Vulnrichment guide</a> shows where they sit and how to pull them with jq.</li>
</ul>
<p>The SSVC documentation describes Exploitation as &ldquo;the present state of exploitation&rdquo;, not a prediction. A <code>none</code> from months ago can be stale, so a KEV listing should outrank an older ADP value. That is the rule our script applies.</p>
<h2 id="step-5-add-epss-for-likelihood">Step 5: add EPSS for likelihood</h2>
<p>For findings with no exploitation evidence, EPSS estimates &ldquo;the probability [0-1] of exploitation in the wild in the next 30 days&rdquo;, and <code>percentile</code> gives the share of scored CVEs with the same or a lower score. The file we used (model v2026.06.15, scored 2026-11-01) held 398,784 CVEs. EPSS is a ranking aid within the non-exploited queue. It does not replace step 4: in our run the KEV-listed FortiMail flaw scored 0.04573. See the <a href="/posts/epss-data-feed-columns-percentile-vs-probability-and-how-to-join-it-to-a-scanner-export/">EPSS data feed guide</a> for the columns, model-version breaks and a scanner join.</p>
<h2 id="step-6-let-exposure-and-impact-decide">Step 6: let exposure and impact decide</h2>
<p>CERT/CC&rsquo;s SSVC deployer model maps four inputs to a patch priority:</p>
<table>
  <thead>
      <tr>
          <th>Input</th>
          <th>Values</th>
          <th>Who supplies it</th>
      </tr>
  </thead>
  <tbody>
      <tr>
          <td>Exploitation</td>
          <td>none, public poc, active</td>
          <td>CISA ADP or KEV, or your own research</td>
      </tr>
      <tr>
          <td>System Exposure</td>
          <td>small, controlled, open</td>
          <td>You, per asset</td>
      </tr>
      <tr>
          <td>Automatable</td>
          <td>no, yes</td>
          <td>CISA ADP, or your own analysis</td>
      </tr>
      <tr>
          <td>Human Impact</td>
          <td>low, medium, high, very high</td>
          <td>You, per asset</td>
      </tr>
  </tbody>
</table>
<p>The decision table (<code>deployer_patch_application_priority_1_0_0.csv</code>, 72 rows) returns one of four outcomes, which the deployer documentation defines as: Defer (&ldquo;Do not act at present&rdquo;), Scheduled (&ldquo;Act during regularly scheduled maintenance time&rdquo;), Out-of-cycle (&ldquo;Act more quickly than usual&hellip; during the next available opportunity&rdquo;) and Immediate (&ldquo;Act immediately; focus all resources on applying the fix&rdquo;). In the table, Immediate appears in 3 rows, all with active exploitation and open exposure. Our <a href="/posts/ssvc-deployer-patch-priority-model-explained-exploitation-exposure-automatable-and-human-impact/">SSVC deployer explainer</a> walks through the inputs, including where Human Impact is easy to get wrong.</p>
<p>One mapping detail: CISA&rsquo;s ADP data writes <code>poc</code>, while the deployer table uses <code>public poc</code>. They are not identical definitions. CISA&rsquo;s tree uses the older PoC value, which also covers privately attested exploitation and widespread hearsay; the newer Public PoC value covers only public exploit code or a well-known method. Our script maps one to the other, which can understate cases CISA marked <code>poc</code> on private evidence.</p>
<h2 id="a-tested-script-that-writes-the-ticket-fields">A tested script that writes the ticket fields</h2>
<p>The script reads a findings CSV, the KEV JSON, the EPSS daily file, the SSVC deployer CSV, a folder of CVE records and an optional OpenVEX file, and prints one ticket row per finding. Python 3.10 or later, standard library only.</p>
<div class="highlight"><pre tabindex="0" style="color:#f8f8f2;background-color:#272822;-moz-tab-size:4;-o-tab-size:4;tab-size:4;"><code class="language-python" data-lang="python"><span style="display:flex;"><span><span style="color:#75715e">#!/usr/bin/env python3</span>
</span></span><span style="display:flex;"><span><span style="color:#e6db74">&#34;&#34;&#34;Turn scanner findings into patch-decision ticket rows.
</span></span></span><span style="display:flex;"><span><span style="color:#e6db74">
</span></span></span><span style="display:flex;"><span><span style="color:#e6db74">Inputs : findings.csv (asset,product,cve,exposure,human_impact)
</span></span></span><span style="display:flex;"><span><span style="color:#e6db74">         KEV JSON, EPSS daily CSV (.csv.gz), SSVC deployer table CSV,
</span></span></span><span style="display:flex;"><span><span style="color:#e6db74">         a directory of cvelistV5 records, optional OpenVEX file.
</span></span></span><span style="display:flex;"><span><span style="color:#e6db74">Output : tickets.csv on stdout. Python 3.10+, standard library only.
</span></span></span><span style="display:flex;"><span><span style="color:#e6db74">&#34;&#34;&#34;</span>
</span></span><span style="display:flex;"><span><span style="color:#f92672">import</span> csv<span style="color:#f92672">,</span> gzip<span style="color:#f92672">,</span> json<span style="color:#f92672">,</span> sys<span style="color:#f92672">,</span> argparse<span style="color:#f92672">,</span> pathlib
</span></span><span style="display:flex;"><span>
</span></span><span style="display:flex;"><span><span style="color:#66d9ef">def</span> <span style="color:#a6e22e">load_kev</span>(path):
</span></span><span style="display:flex;"><span>    data <span style="color:#f92672">=</span> json<span style="color:#f92672">.</span>load(open(path))
</span></span><span style="display:flex;"><span>    <span style="color:#66d9ef">return</span> {v[<span style="color:#e6db74">&#34;cveID&#34;</span>]<span style="color:#f92672">.</span>strip()<span style="color:#f92672">.</span>upper(): v <span style="color:#66d9ef">for</span> v <span style="color:#f92672">in</span> data[<span style="color:#e6db74">&#34;vulnerabilities&#34;</span>]}
</span></span><span style="display:flex;"><span>
</span></span><span style="display:flex;"><span><span style="color:#66d9ef">def</span> <span style="color:#a6e22e">load_epss</span>(path):
</span></span><span style="display:flex;"><span>    scores <span style="color:#f92672">=</span> {}
</span></span><span style="display:flex;"><span>    <span style="color:#66d9ef">with</span> gzip<span style="color:#f92672">.</span>open(path, <span style="color:#e6db74">&#34;rt&#34;</span>) <span style="color:#66d9ef">as</span> fh:
</span></span><span style="display:flex;"><span>        rows <span style="color:#f92672">=</span> (line <span style="color:#66d9ef">for</span> line <span style="color:#f92672">in</span> fh <span style="color:#66d9ef">if</span> <span style="color:#f92672">not</span> line<span style="color:#f92672">.</span>startswith(<span style="color:#e6db74">&#34;#&#34;</span>))
</span></span><span style="display:flex;"><span>        <span style="color:#66d9ef">for</span> r <span style="color:#f92672">in</span> csv<span style="color:#f92672">.</span>DictReader(rows):
</span></span><span style="display:flex;"><span>            scores[r[<span style="color:#e6db74">&#34;cve&#34;</span>]] <span style="color:#f92672">=</span> (float(r[<span style="color:#e6db74">&#34;epss&#34;</span>]), float(r[<span style="color:#e6db74">&#34;percentile&#34;</span>]))
</span></span><span style="display:flex;"><span>    <span style="color:#66d9ef">return</span> scores
</span></span><span style="display:flex;"><span>
</span></span><span style="display:flex;"><span><span style="color:#66d9ef">def</span> <span style="color:#a6e22e">load_deployer</span>(path):
</span></span><span style="display:flex;"><span>    rows <span style="color:#f92672">=</span> list(csv<span style="color:#f92672">.</span>reader(open(path)))
</span></span><span style="display:flex;"><span>    <span style="color:#66d9ef">return</span> {tuple(r[<span style="color:#ae81ff">1</span>:<span style="color:#ae81ff">5</span>]): r[<span style="color:#ae81ff">5</span>] <span style="color:#66d9ef">for</span> r <span style="color:#f92672">in</span> rows[<span style="color:#ae81ff">1</span>:]}
</span></span><span style="display:flex;"><span>
</span></span><span style="display:flex;"><span><span style="color:#66d9ef">def</span> <span style="color:#a6e22e">load_vex</span>(path):
</span></span><span style="display:flex;"><span>    out <span style="color:#f92672">=</span> {}
</span></span><span style="display:flex;"><span>    <span style="color:#66d9ef">if</span> path:
</span></span><span style="display:flex;"><span>        <span style="color:#66d9ef">for</span> s <span style="color:#f92672">in</span> json<span style="color:#f92672">.</span>load(open(path))<span style="color:#f92672">.</span>get(<span style="color:#e6db74">&#34;statements&#34;</span>, []):
</span></span><span style="display:flex;"><span>            <span style="color:#66d9ef">for</span> p <span style="color:#f92672">in</span> s<span style="color:#f92672">.</span>get(<span style="color:#e6db74">&#34;products&#34;</span>, []):
</span></span><span style="display:flex;"><span>                out[(s[<span style="color:#e6db74">&#34;vulnerability&#34;</span>][<span style="color:#e6db74">&#34;name&#34;</span>]<span style="color:#f92672">.</span>upper(), p[<span style="color:#e6db74">&#34;@id&#34;</span>])] <span style="color:#f92672">=</span> s
</span></span><span style="display:flex;"><span>    <span style="color:#66d9ef">return</span> out
</span></span><span style="display:flex;"><span>
</span></span><span style="display:flex;"><span><span style="color:#66d9ef">def</span> <span style="color:#a6e22e">cisa_ssvc</span>(record):
</span></span><span style="display:flex;"><span>    <span style="color:#e6db74">&#34;&#34;&#34;Return CISA ADP SSVC values (Exploitation, Automatable, Technical Impact, timestamp).&#34;&#34;&#34;</span>
</span></span><span style="display:flex;"><span>    <span style="color:#66d9ef">for</span> adp <span style="color:#f92672">in</span> record[<span style="color:#e6db74">&#34;containers&#34;</span>]<span style="color:#f92672">.</span>get(<span style="color:#e6db74">&#34;adp&#34;</span>, []):
</span></span><span style="display:flex;"><span>        <span style="color:#66d9ef">for</span> m <span style="color:#f92672">in</span> adp<span style="color:#f92672">.</span>get(<span style="color:#e6db74">&#34;metrics&#34;</span>, []):
</span></span><span style="display:flex;"><span>            other <span style="color:#f92672">=</span> m<span style="color:#f92672">.</span>get(<span style="color:#e6db74">&#34;other&#34;</span>, {})
</span></span><span style="display:flex;"><span>            <span style="color:#66d9ef">if</span> other<span style="color:#f92672">.</span>get(<span style="color:#e6db74">&#34;type&#34;</span>) <span style="color:#f92672">==</span> <span style="color:#e6db74">&#34;ssvc&#34;</span>:
</span></span><span style="display:flex;"><span>                c <span style="color:#f92672">=</span> other[<span style="color:#e6db74">&#34;content&#34;</span>]
</span></span><span style="display:flex;"><span>                opts <span style="color:#f92672">=</span> {k: v <span style="color:#66d9ef">for</span> o <span style="color:#f92672">in</span> c[<span style="color:#e6db74">&#34;options&#34;</span>] <span style="color:#66d9ef">for</span> k, v <span style="color:#f92672">in</span> o<span style="color:#f92672">.</span>items()}
</span></span><span style="display:flex;"><span>                <span style="color:#66d9ef">return</span> (opts<span style="color:#f92672">.</span>get(<span style="color:#e6db74">&#34;Exploitation&#34;</span>), opts<span style="color:#f92672">.</span>get(<span style="color:#e6db74">&#34;Automatable&#34;</span>),
</span></span><span style="display:flex;"><span>                        opts<span style="color:#f92672">.</span>get(<span style="color:#e6db74">&#34;Technical Impact&#34;</span>), c<span style="color:#f92672">.</span>get(<span style="color:#e6db74">&#34;timestamp&#34;</span>))
</span></span><span style="display:flex;"><span>    <span style="color:#66d9ef">return</span> (<span style="color:#66d9ef">None</span>, <span style="color:#66d9ef">None</span>, <span style="color:#66d9ef">None</span>, <span style="color:#66d9ef">None</span>)
</span></span><span style="display:flex;"><span>
</span></span><span style="display:flex;"><span><span style="color:#66d9ef">def</span> <span style="color:#a6e22e">main</span>():
</span></span><span style="display:flex;"><span>    ap <span style="color:#f92672">=</span> argparse<span style="color:#f92672">.</span>ArgumentParser()
</span></span><span style="display:flex;"><span>    <span style="color:#66d9ef">for</span> a <span style="color:#f92672">in</span> (<span style="color:#e6db74">&#34;findings&#34;</span>, <span style="color:#e6db74">&#34;kev&#34;</span>, <span style="color:#e6db74">&#34;epss&#34;</span>, <span style="color:#e6db74">&#34;deployer&#34;</span>, <span style="color:#e6db74">&#34;records&#34;</span>):
</span></span><span style="display:flex;"><span>        ap<span style="color:#f92672">.</span>add_argument(a)
</span></span><span style="display:flex;"><span>    ap<span style="color:#f92672">.</span>add_argument(<span style="color:#e6db74">&#34;--vex&#34;</span>)
</span></span><span style="display:flex;"><span>    args <span style="color:#f92672">=</span> ap<span style="color:#f92672">.</span>parse_args()
</span></span><span style="display:flex;"><span>    kev, epss <span style="color:#f92672">=</span> load_kev(args<span style="color:#f92672">.</span>kev), load_epss(args<span style="color:#f92672">.</span>epss)
</span></span><span style="display:flex;"><span>    table, vex <span style="color:#f92672">=</span> load_deployer(args<span style="color:#f92672">.</span>deployer), load_vex(args<span style="color:#f92672">.</span>vex)
</span></span><span style="display:flex;"><span>    out <span style="color:#f92672">=</span> csv<span style="color:#f92672">.</span>writer(sys<span style="color:#f92672">.</span>stdout)
</span></span><span style="display:flex;"><span>    out<span style="color:#f92672">.</span>writerow([<span style="color:#e6db74">&#34;asset&#34;</span>, <span style="color:#e6db74">&#34;cve&#34;</span>, <span style="color:#e6db74">&#34;record_state&#34;</span>, <span style="color:#e6db74">&#34;vex_status&#34;</span>, <span style="color:#e6db74">&#34;kev_dateAdded&#34;</span>,
</span></span><span style="display:flex;"><span>                  <span style="color:#e6db74">&#34;kev_dueDate&#34;</span>, <span style="color:#e6db74">&#34;kev_ransomware&#34;</span>, <span style="color:#e6db74">&#34;cisa_exploitation&#34;</span>, <span style="color:#e6db74">&#34;cisa_automatable&#34;</span>,
</span></span><span style="display:flex;"><span>                  <span style="color:#e6db74">&#34;cisa_technical_impact&#34;</span>, <span style="color:#e6db74">&#34;cisa_ssvc_timestamp&#34;</span>, <span style="color:#e6db74">&#34;epss&#34;</span>, <span style="color:#e6db74">&#34;epss_percentile&#34;</span>,
</span></span><span style="display:flex;"><span>                  <span style="color:#e6db74">&#34;deployer_exploitation&#34;</span>, <span style="color:#e6db74">&#34;deployer_priority&#34;</span>, <span style="color:#e6db74">&#34;next_step&#34;</span>])
</span></span><span style="display:flex;"><span>    <span style="color:#66d9ef">for</span> f <span style="color:#f92672">in</span> csv<span style="color:#f92672">.</span>DictReader(open(args<span style="color:#f92672">.</span>findings)):
</span></span><span style="display:flex;"><span>        cve <span style="color:#f92672">=</span> f[<span style="color:#e6db74">&#34;cve&#34;</span>]<span style="color:#f92672">.</span>strip()<span style="color:#f92672">.</span>upper()
</span></span><span style="display:flex;"><span>        rec_path <span style="color:#f92672">=</span> pathlib<span style="color:#f92672">.</span>Path(args<span style="color:#f92672">.</span>records) <span style="color:#f92672">/</span> <span style="color:#e6db74">f</span><span style="color:#e6db74">&#34;</span><span style="color:#e6db74">{</span>cve<span style="color:#e6db74">}</span><span style="color:#e6db74">.json&#34;</span>
</span></span><span style="display:flex;"><span>        <span style="color:#66d9ef">if</span> <span style="color:#f92672">not</span> rec_path<span style="color:#f92672">.</span>exists():
</span></span><span style="display:flex;"><span>            out<span style="color:#f92672">.</span>writerow([f[<span style="color:#e6db74">&#34;asset&#34;</span>], cve, <span style="color:#e6db74">&#34;NO RECORD&#34;</span>] <span style="color:#f92672">+</span> [<span style="color:#e6db74">&#34;&#34;</span>] <span style="color:#f92672">*</span> <span style="color:#ae81ff">12</span> <span style="color:#f92672">+</span> [<span style="color:#e6db74">&#34;check the ID&#34;</span>])
</span></span><span style="display:flex;"><span>            <span style="color:#66d9ef">continue</span>
</span></span><span style="display:flex;"><span>        rec <span style="color:#f92672">=</span> json<span style="color:#f92672">.</span>load(open(rec_path))
</span></span><span style="display:flex;"><span>        state <span style="color:#f92672">=</span> rec[<span style="color:#e6db74">&#34;cveMetadata&#34;</span>][<span style="color:#e6db74">&#34;state&#34;</span>]
</span></span><span style="display:flex;"><span>        <span style="color:#66d9ef">if</span> state <span style="color:#f92672">==</span> <span style="color:#e6db74">&#34;REJECTED&#34;</span>:
</span></span><span style="display:flex;"><span>            out<span style="color:#f92672">.</span>writerow([f[<span style="color:#e6db74">&#34;asset&#34;</span>], cve, state] <span style="color:#f92672">+</span> [<span style="color:#e6db74">&#34;&#34;</span>] <span style="color:#f92672">*</span> <span style="color:#ae81ff">12</span> <span style="color:#f92672">+</span> [<span style="color:#e6db74">&#34;close: CVE ID rejected&#34;</span>])
</span></span><span style="display:flex;"><span>            <span style="color:#66d9ef">continue</span>
</span></span><span style="display:flex;"><span>        v <span style="color:#f92672">=</span> vex<span style="color:#f92672">.</span>get((cve, f<span style="color:#f92672">.</span>get(<span style="color:#e6db74">&#34;product&#34;</span>, <span style="color:#e6db74">&#34;&#34;</span>)), {})  <span style="color:#75715e"># VEX applies to one product, not every asset</span>
</span></span><span style="display:flex;"><span>        k <span style="color:#f92672">=</span> kev<span style="color:#f92672">.</span>get(cve, {})
</span></span><span style="display:flex;"><span>        exp, auto, ti, ts <span style="color:#f92672">=</span> cisa_ssvc(rec)
</span></span><span style="display:flex;"><span>        e, pct <span style="color:#f92672">=</span> epss<span style="color:#f92672">.</span>get(cve, (<span style="color:#e6db74">&#34;&#34;</span>, <span style="color:#e6db74">&#34;&#34;</span>))
</span></span><span style="display:flex;"><span>        <span style="color:#75715e"># Our policy choice: a KEV listing counts as active exploitation, whatever</span>
</span></span><span style="display:flex;"><span>        <span style="color:#75715e"># the (possibly older) CISA ADP snapshot says. CISA writes &#34;poc&#34;; the</span>
</span></span><span style="display:flex;"><span>        <span style="color:#75715e"># deployer table writes &#34;public poc&#34;.</span>
</span></span><span style="display:flex;"><span>        dexp <span style="color:#f92672">=</span> <span style="color:#e6db74">&#34;active&#34;</span> <span style="color:#66d9ef">if</span> k <span style="color:#66d9ef">else</span> {<span style="color:#e6db74">&#34;poc&#34;</span>: <span style="color:#e6db74">&#34;public poc&#34;</span>}<span style="color:#f92672">.</span>get(exp, exp)
</span></span><span style="display:flex;"><span>        prio <span style="color:#f92672">=</span> <span style="color:#e6db74">&#34;&#34;</span>
</span></span><span style="display:flex;"><span>        <span style="color:#66d9ef">if</span> dexp <span style="color:#f92672">and</span> auto:
</span></span><span style="display:flex;"><span>            prio <span style="color:#f92672">=</span> table<span style="color:#f92672">.</span>get((dexp, f[<span style="color:#e6db74">&#34;exposure&#34;</span>], auto, f[<span style="color:#e6db74">&#34;human_impact&#34;</span>]), <span style="color:#e6db74">&#34;&#34;</span>)
</span></span><span style="display:flex;"><span>        <span style="color:#66d9ef">if</span> v<span style="color:#f92672">.</span>get(<span style="color:#e6db74">&#34;status&#34;</span>) <span style="color:#f92672">==</span> <span style="color:#e6db74">&#34;not_affected&#34;</span>:
</span></span><span style="display:flex;"><span>            step <span style="color:#f92672">=</span> <span style="color:#e6db74">&#34;close: supplier VEX not_affected (&#34;</span> <span style="color:#f92672">+</span> v<span style="color:#f92672">.</span>get(<span style="color:#e6db74">&#34;justification&#34;</span>, <span style="color:#e6db74">&#34;no justification&#34;</span>) <span style="color:#f92672">+</span> <span style="color:#e6db74">&#34;)&#34;</span>
</span></span><span style="display:flex;"><span>        <span style="color:#66d9ef">elif</span> <span style="color:#f92672">not</span> prio:
</span></span><span style="display:flex;"><span>            step <span style="color:#f92672">=</span> <span style="color:#e6db74">&#34;manual triage: no CISA SSVC data&#34;</span>
</span></span><span style="display:flex;"><span>        <span style="color:#66d9ef">else</span>:
</span></span><span style="display:flex;"><span>            step <span style="color:#f92672">=</span> prio
</span></span><span style="display:flex;"><span>        out<span style="color:#f92672">.</span>writerow([f[<span style="color:#e6db74">&#34;asset&#34;</span>], cve, state, v<span style="color:#f92672">.</span>get(<span style="color:#e6db74">&#34;status&#34;</span>, <span style="color:#e6db74">&#34;&#34;</span>), k<span style="color:#f92672">.</span>get(<span style="color:#e6db74">&#34;dateAdded&#34;</span>, <span style="color:#e6db74">&#34;&#34;</span>),
</span></span><span style="display:flex;"><span>                      k<span style="color:#f92672">.</span>get(<span style="color:#e6db74">&#34;dueDate&#34;</span>, <span style="color:#e6db74">&#34;&#34;</span>), k<span style="color:#f92672">.</span>get(<span style="color:#e6db74">&#34;knownRansomwareCampaignUse&#34;</span>, <span style="color:#e6db74">&#34;&#34;</span>),
</span></span><span style="display:flex;"><span>                      exp <span style="color:#f92672">or</span> <span style="color:#e6db74">&#34;&#34;</span>, auto <span style="color:#f92672">or</span> <span style="color:#e6db74">&#34;&#34;</span>, ti <span style="color:#f92672">or</span> <span style="color:#e6db74">&#34;&#34;</span>, ts <span style="color:#f92672">or</span> <span style="color:#e6db74">&#34;&#34;</span>, e, pct, dexp <span style="color:#f92672">or</span> <span style="color:#e6db74">&#34;&#34;</span>, prio, step])
</span></span><span style="display:flex;"><span>
</span></span><span style="display:flex;"><span><span style="color:#66d9ef">if</span> __name__ <span style="color:#f92672">==</span> <span style="color:#e6db74">&#34;__main__&#34;</span>:
</span></span><span style="display:flex;"><span>    main()
</span></span></code></pre></div><p>The test input (<code>findings.csv</code>) used invented assets with real CVE IDs:</p>
<div class="highlight"><pre tabindex="0" style="color:#f8f8f2;background-color:#272822;-moz-tab-size:4;-o-tab-size:4;tab-size:4;"><code class="language-text" data-lang="text"><span style="display:flex;"><span>asset,product,cve,exposure,human_impact
</span></span><span style="display:flex;"><span>edge-mail-01,fortimail,CVE-2026-104286,open,high
</span></span><span style="display:flex;"><span>k8s-node-17,linux-kernel,CVE-2026-46300,controlled,medium
</span></span><span style="display:flex;"><span>build-runner-03,pkg:cargo/gix-fs@0.22.1,CVE-2026-100419,small,medium
</span></span><span style="display:flex;"><span>billing-api,pkg:maven/org.apache.logging.log4j/log4j-core@2.14.1,CVE-2021-44228,open,very high
</span></span><span style="display:flex;"><span>vendor-appliance-2,pkg:generic/example-appliance@4.2,CVE-2021-44228,open,very high
</span></span><span style="display:flex;"><span>legacy-scan,unknown,CVE-2026-23915,open,low
</span></span></code></pre></div><p>The VEX file is an invented OpenVEX document from an &ldquo;Example Appliance Vendor&rdquo; stating <code>not_affected</code> with justification <code>vulnerable_code_not_present</code> for CVE-2021-44228 in <code>pkg:generic/example-appliance@4.2</code>. We ran:</p>
<div class="highlight"><pre tabindex="0" style="color:#f8f8f2;background-color:#272822;-moz-tab-size:4;-o-tab-size:4;tab-size:4;"><code class="language-bash" data-lang="bash"><span style="display:flex;"><span>python3 patch_decision.py findings.csv known_exploited_vulnerabilities.json <span style="color:#ae81ff">\
</span></span></span><span style="display:flex;"><span><span style="color:#ae81ff"></span>  epss_scores-2026-11-01.csv.gz deployer_patch_application_priority_1_0_0.csv <span style="color:#ae81ff">\
</span></span></span><span style="display:flex;"><span><span style="color:#ae81ff"></span>  records/ --vex vendor.openvex.json &gt; tickets.csv
</span></span></code></pre></div><p>The data came from <code>raw.githubusercontent.com/cisagov/kev-data</code>, the <code>empiricalsec/epss_scores</code> repository (2026/epss_scores-2026-11-01.csv.gz), <code>CERTCC/SSVC</code> (data/csv/ssvc/) and <code>CVEProject/cvelistV5</code> at commit 451e97a. Output, with some columns dropped for width:</p>
<table>
  <thead>
      <tr>
          <th>Asset</th>
          <th>CVE</th>
          <th>KEV added</th>
          <th>CISA SSVC (E / A / TI)</th>
          <th>EPSS (percentile)</th>
          <th>Deployer priority</th>
          <th>Next step</th>
      </tr>
  </thead>
  <tbody>
      <tr>
          <td>edge-mail-01</td>
          <td>CVE-2026-104286</td>
          <td>2026-10-01</td>
          <td>active / yes / total</td>
          <td>0.04573 (0.916)</td>
          <td>immediate</td>
          <td>immediate</td>
      </tr>
      <tr>
          <td>k8s-node-17</td>
          <td>CVE-2026-46300</td>
          <td>2026-10-28</td>
          <td>active / no / total</td>
          <td>0.1613 (0.969)</td>
          <td>scheduled</td>
          <td>scheduled</td>
      </tr>
      <tr>
          <td>build-runner-03</td>
          <td>CVE-2026-100419</td>
          <td>-</td>
          <td>poc / no / total</td>
          <td>0.00222 (0.129)</td>
          <td>scheduled</td>
          <td>scheduled</td>
      </tr>
      <tr>
          <td>billing-api</td>
          <td>CVE-2021-44228</td>
          <td>2021-12-10</td>
          <td>active / yes / total</td>
          <td>0.99999 (1.0)</td>
          <td>immediate</td>
          <td>immediate</td>
      </tr>
      <tr>
          <td>vendor-appliance-2</td>
          <td>CVE-2021-44228</td>
          <td>2021-12-10</td>
          <td>active / yes / total</td>
          <td>0.99999 (1.0)</td>
          <td>immediate</td>
          <td>close: supplier VEX not_affected (vulnerable_code_not_present)</td>
      </tr>
      <tr>
          <td>legacy-scan</td>
          <td>CVE-2026-23915</td>
          <td>-</td>
          <td>-</td>
          <td>-</td>
          <td>-</td>
          <td>close: CVE ID rejected</td>
      </tr>
  </tbody>
</table>
<p>Three things in that output are worth noticing:</p>
<ul>
<li><strong>The same CVE got two different answers</strong> (Log4Shell rows) because the VEX statement applies to one product only.</li>
<li><strong>A KEV-listed kernel flaw came out Scheduled.</strong> CVE-2026-46300 is in KEV with <code>forensicTriage: Yes</code> and a three-day federal due date, but with controlled exposure, no automatability and medium Human Impact the deployer table says Scheduled. If you follow CISA&rsquo;s directives, the due date wins. If you do not, the table is telling you the exposure is what drives urgency. Either way, keep both fields in the ticket, and consider a compromise check when <code>forensicTriage</code> is Yes; our <a href="/posts/cisa-bod-26-04-explained-kev-deadlines-forensic-triage-and-what-private-teams-can-borrow/">BOD 26-04 explainer</a> covers what that flag asks agencies to do.</li>
<li><strong>EPSS and KEV disagreed</strong> on FortiMail, as expected: one estimates future observed activity, the other records evidence already seen.</li>
</ul>
<h2 id="what-the-ticket-should-hold">What the ticket should hold</h2>
<p>Store the inputs, not just the priority, so a reviewer can see why. A suggested field list (ours, not a standard):</p>
<table>
  <thead>
      <tr>
          <th>Field</th>
          <th>Why</th>
      </tr>
  </thead>
  <tbody>
      <tr>
          <td>Asset, product identifier (purl or CPE), version</td>
          <td>Ties VEX and affected checks to the right thing</td>
      </tr>
      <tr>
          <td>CVE ID, record state, record <code>dateUpdated</code></td>
          <td>Detects rejected IDs and record changes</td>
      </tr>
      <tr>
          <td>Affected status and how it was decided</td>
          <td>&ldquo;unknown&rdquo; needs a different owner from &ldquo;affected&rdquo;</td>
      </tr>
      <tr>
          <td>VEX status, justification, document author and timestamp</td>
          <td>Audit trail for closures</td>
      </tr>
      <tr>
          <td>KEV <code>dateAdded</code>, <code>dueDate</code>, <code>knownRansomwareCampaignUse</code>, <code>forensicTriage</code></td>
          <td>Exploitation evidence and any federal deadline</td>
      </tr>
      <tr>
          <td>CISA SSVC Exploitation, Automatable, Technical Impact, timestamp</td>
          <td>Shows how fresh the assessment is</td>
      </tr>
      <tr>
          <td>EPSS score, percentile, model version, score date</td>
          <td>Scores shift when the model changes</td>
      </tr>
      <tr>
          <td>Your System Exposure and Human Impact</td>
          <td>The inputs only you can supply</td>
      </tr>
      <tr>
          <td>Priority and data pull date</td>
          <td>Lets you re-run and compare</td>
      </tr>
  </tbody>
</table>
<h2 id="keeping-it-current">Keeping it current</h2>
<p>The feeds move at different speeds: CISA updates KEV on weekdays, EPSS publishes daily, and CVE records and VEX documents change when their authors revise them. Re-run the flow on a schedule and on any change to a ticket&rsquo;s inputs, and alert when a finding&rsquo;s priority rises. Set your service-level targets per priority (for example, how many days &ldquo;Out-of-cycle&rdquo; means for you) in policy, not in the script; the deployer model does not define days.</p>
<h2 id="limits-of-this-article">Limits of this article</h2>
<p>The script is a working example, not a product. It reads CVE records from a local folder (it does not fetch them), does not evaluate affected versions itself (pair it with a version check such as the evaluator in our affected-versions guide), handles OpenVEX JSON only, and uses one policy choice (KEV overrides an older CISA Exploitation value) that you may want to change. The four-value deployer inputs simplify real decisions: SSVC expects organizations to adapt trees to their context. We did not test it against commercial scanner exports.</p>
<h2 id="sources-and-verification">Sources and verification</h2>
<table>
  <thead>
      <tr>
          <th>Important claim</th>
          <th>Source</th>
          <th>Status</th>
      </tr>
  </thead>
  <tbody>
      <tr>
          <td>CVE record states, <code>affected</code> algorithm, <code>defaultStatus</code> defaults to unknown</td>
          <td><a href="https://github.com/CVEProject/cve-schema/blob/main/schema/CVE_Record_Format.json">CVE JSON schema (CVE_Record_Format.json, 5.2.0)</a></td>
          <td>Verified</td>
      </tr>
      <tr>
          <td>CVE-2026-23915 rejected, reason &ldquo;Not used&rdquo;; SSVC values and timestamps for the test CVEs</td>
          <td><a href="https://github.com/CVEProject/cvelistV5">cvelistV5</a>, commit 451e97a</td>
          <td>Verified (read November 2, 2026)</td>
      </tr>
      <tr>
          <td>Vulnrichment assesses &ldquo;new and recent CVEs&rdquo;, adds SSVC decision points, never overwrites CNA data</td>
          <td><a href="https://github.com/cisagov/vulnrichment">cisagov/vulnrichment README</a></td>
          <td>Verified</td>
      </tr>
      <tr>
          <td>KEV catalog 2026.10.30, 1,766 entries; dates and flags for the test CVEs</td>
          <td><a href="https://github.com/cisagov/kev-data">cisagov/kev-data</a></td>
          <td>Verified</td>
      </tr>
      <tr>
          <td>EPSS field definitions; file model v2026.06.15, 398,784 CVEs; scores for the test CVEs</td>
          <td><a href="https://github.com/empiricalsec/epss_scores">empiricalsec/epss_scores</a></td>
          <td>Verified (computed from the file)</td>
      </tr>
      <tr>
          <td>Deployer inputs, values, 72-row table, outcome definitions, active never Defer</td>
          <td><a href="https://github.com/CERTCC/SSVC/blob/main/docs/howto/deployer_tree.md">CERT/CC SSVC deployer tree</a> and <a href="https://github.com/CERTCC/SSVC/blob/main/data/csv/ssvc/deployer_patch_application_priority_1_0_0.csv">decision table CSV</a></td>
          <td>Verified</td>
      </tr>
      <tr>
          <td>Exploitation is &ldquo;the present state of exploitation&rdquo;; PoC vs Public PoC definitions</td>
          <td><a href="https://github.com/CERTCC/SSVC/blob/main/docs/reference/decision_points/exploitation.md">SSVC Exploitation decision point</a> and its source definitions</td>
          <td>Verified</td>
      </tr>
      <tr>
          <td>OpenVEX statuses and the justification requirement</td>
          <td><a href="https://github.com/openvex/spec/blob/main/OPENVEX-SPEC.md">OpenVEX specification</a></td>
          <td>Verified</td>
      </tr>
      <tr>
          <td>Script output</td>
          <td>Script above, Python 3.13, run November 2, 2026</td>
          <td>Verified</td>
      </tr>
  </tbody>
</table>
]]></content:encoded></item></channel></rss>