Scope. 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’s GitHub repository, Red Hat’s July 2024 announcement of its CSAF VEX files, and Trivy’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.

The short answer

A CSAF VEX file never puts a purl next to a status. It says “product ID GW-4.2.1:LIB-1.8.0 is known_not_affected”, and you have to work out what that ID is:

1. Find the ID in the product_tree: at the end of a branches path, in full_product_names, or as the full_product_name of a relationships entry.
2. If it is a relationship, resolve both sides: product_reference (the component) and relates_to_product_reference (the product it sits in).
3. Read product_identification_helper.purl (or cpe) for each side.
4. Apply the status only when your SBOM contains the component and the parent matches the product you are assessing.
5. Collapse the eight product_status lists to the four VEX answers before you write anything to a ticket.

The rest of this article goes through each step, shows a schema-valid example, and gives a script that does the join.

What the VEX profile requires

CSAF 2.0 has been an OASIS Standard since 18 November 2022. The VEX profile is section 4.5. A document satisfies it when /document/category is csaf_vex and it contains:

• a product_tree “which lists all products referenced later on in the CSAF document regardless of their state”;
• vulnerabilities, each with notes and at least one of cve or ids;
• at least one of the fixed, known_affected, known_not_affected or under_investigation lists.

Two conditions are per product, and they are the ones consumers should check:

• Every product in known_not_affected needs an impact statement, either “as machine readable flag in /vulnerabilities[]/flags or as human readable justification in /vulnerabilities[]/threats” with category set to impact.
• Every product in known_affected needs “additional product specific information” in remediations “as an action statement”. The categories no_fix_planned and none_available count.

The five flag labels are the CISA justification codes: component_not_present, vulnerable_code_not_present, vulnerable_code_cannot_be_controlled_by_adversary, vulnerable_code_not_in_execute_path and inline_mitigations_already_exist. If you need the meaning of each one, the VEX explainer covers them. The CycloneDX VEX mapping guide 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.

Step 1: walk the product tree

The product_tree can name products in three places. A consumer has to read all three.

Every one of these is a “full product name”: name and product_id are required, and product_identification_helper is optional. That helper is where purl, cpe, hashes and SBOM URLs go. The CSAF schema only checks the purl against a loose pattern (^pkg:[A-Za-z\.\-\+][A-Za-z0-9\.\-\+]*/.+) and says it “does not completely evaluate whether a PURL is valid”, so validate purls yourself before matching on them.

There is also product_groups, which bundles product IDs under a group ID. Product status lists only hold product IDs, but flags, threats and remediations can reference groups through group_ids, so expand groups when you collect impact and action statements.

The spec recommends the vendor → product_name → product_version shape “whenever possible to support the identification and matching of products on the consumer side”. It also allows product_version_range 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.

Step 2: treat relationships as “component in product”

A relationship has four required fields: category, product_reference, relates_to_product_reference and full_product_name. The categories are default_component_of, external_component_of, installed_on, installed_with and optional_component_of. The spec gives the reason relationships exist: a product may be “vulnerable only when installed together with another”, or you may need “to describe operating system components”.

This is the part consumers get wrong. In our example below, LIB-1.8.0 is the library on its own and GW-4.2.1:LIB-1.8.0 is “libexample 1.8.0 as shipped in Example Gateway 4.2.1”. A vendor that marks the second ID known_not_affected 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.

The rule we use: for a relationship ID, apply the status only when the component purl matches a component in the SBOM and the parent purl matches the SBOM’s subject (for CycloneDX, metadata.component).

Red Hat’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 product_tree object listing “products, their components, and the relationships between them”. In the general-availability release Red Hat “extended the scope of the purl identifiers to unfixed components as well” for rpm, oci and rpmmod components. In the October 2023 beta, only fixed components carried a purl. Check which one you are parsing.

Step 3: collapse eight status lists into four answers

CSAF defines eight product_status lists. VEX consumers need four answers. The spec’s own test for contradicting statuses (section 6.1.6) gives the grouping, and the sets “MUST be pairwise disjoint” within one vulnerability:

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.

For affected products, the remediation categories tell you what kind of action is available: vendor_fix, workaround, mitigation, none_available or no_fix_planned. vendor_fix cannot be combined with none_available or no_fix_planned for the same product.

A schema-valid example

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 jsonschema, Draft 2020-12, format checks on; 0 errors). Schema validation does not run CSAF’s mandatory tests, so it does not prove the profile rules are met. We checked those by hand.

{
  "document": {
    "category": "csaf_vex",
    "csaf_version": "2.0",
    "publisher": {"category": "vendor", "name": "Example Vendor", "namespace": "https://vendor.example"},
    "title": "Example Gateway: CVE-2099-0001 in libexample",
    "tracking": {"id": "EXV-2099-0001", "status": "final", "version": "2", "...": "..."}
  },
  "product_tree": {
    "branches": [{"category": "vendor", "name": "Example Vendor", "branches": [
      {"category": "product_name", "name": "Example Gateway", "branches": [
        {"category": "product_version", "name": "4.2.1",
         "product": {"name": "Example Gateway 4.2.1", "product_id": "GW-4.2.1",
           "product_identification_helper": {"purl": "pkg:oci/example-gateway@sha256%3A1111?tag=4.2.1"}}}
      ]},
      {"category": "product_name", "name": "libexample", "branches": [
        {"category": "product_version", "name": "1.8.0",
         "product": {"name": "libexample 1.8.0", "product_id": "LIB-1.8.0",
           "product_identification_helper": {"purl": "pkg:deb/debian/libexample@1.8.0-1"}}}
      ]}
    ]}],
    "relationships": [
      {"category": "default_component_of",
       "product_reference": "LIB-1.8.0",
       "relates_to_product_reference": "GW-4.2.1",
       "full_product_name": {"name": "libexample 1.8.0 in Example Gateway 4.2.1",
                             "product_id": "GW-4.2.1:LIB-1.8.0"}}
    ]
  },
  "vulnerabilities": [{
    "cve": "CVE-2099-0001",
    "notes": [{"category": "description", "text": "Illustrative vulnerability in libexample's XML parser."}],
    "product_status": {"known_not_affected": ["GW-4.2.1:LIB-1.8.0"], "fixed": ["GW-4.3.0:LIB-1.8.2"]},
    "flags": [{"label": "vulnerable_code_not_in_execute_path", "product_ids": ["GW-4.2.1:LIB-1.8.0"]}],
    "threats": [{"category": "impact", "details": "Example Gateway never calls the XML parser in libexample.",
                 "product_ids": ["GW-4.2.1:LIB-1.8.0"]}]
  }]
}

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.

Step 4: join to the SBOM

The script resolves every product ID in product_status 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 “are not formally defined within the current official PURL specification”: 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.

#!/usr/bin/env python3
"""Resolve CSAF VEX product_status entries to purls and join them to a CycloneDX SBOM.
Illustrative: purl matching follows the rules in purl_match(); no version-range logic."""
import json, sys
from urllib.parse import unquote

def parse(p):
    """Split a purl into (type/namespace/name, version or None, qualifiers dict). Subpath ignored."""
    p = p.split("#")[0]
    core, _, q = p.partition("?")
    quals = dict(kv.split("=", 1) for kv in q.split("&") if "=" in kv)
    path, _, ver = core.rpartition("@") if "@" in core.rsplit("/", 1)[-1] else (core, "", "")
    return unquote(path).lower(), unquote(ver) or None, {k.lower(): unquote(v) for k, v in quals.items()}

def purl_match(vex_purl, sbom_purl):
    """Community matching rules (as documented by Trivy): a VEX purl without a version matches
    every version; VEX qualifiers must all be present in the SBOM purl; extra SBOM qualifiers are ignored."""
    vp, vv, vq = parse(vex_purl)
    sp, sv, sq = parse(sbom_purl)
    return vp == sp and (vv is None or vv == sv) and all(sq.get(k) == v for k, v in vq.items())

def walk_branches(branches, out):
    for b in branches or []:
        if "product" in b:
            fpn = b["product"]
            out[fpn["product_id"]] = fpn.get("product_identification_helper", {}).get("purl")
        walk_branches(b.get("branches"), out)

def load_products(doc):
    tree = doc["product_tree"]
    purls = {}
    walk_branches(tree.get("branches"), purls)
    for fpn in tree.get("full_product_names", []):
        purls[fpn["product_id"]] = fpn.get("product_identification_helper", {}).get("purl")
    rels = {}
    for r in tree.get("relationships", []):
        rels[r["full_product_name"]["product_id"]] = (
            r["category"], r["product_reference"], r["relates_to_product_reference"])
    groups = {g["group_id"]: g["product_ids"] for g in tree.get("product_groups", [])}
    return purls, rels, groups

def main(vex_path, sbom_path):
    doc = json.load(open(vex_path))
    assert doc["document"]["category"] == "csaf_vex", "not a VEX profile document"
    purls, rels, groups = load_products(doc)
    sbom = json.load(open(sbom_path))
    parent = sbom["metadata"]["component"]["purl"]
    inventory = [c["purl"] for c in sbom.get("components", []) if c.get("purl")]
    in_sbom = lambda vex_purl: any(purl_match(vex_purl, s) for s in inventory)

    for v in doc["vulnerabilities"]:
        flags = {pid: f["label"] for f in v.get("flags", [])
                 for pid in f.get("product_ids", []) + sum((groups[g] for g in f.get("group_ids", [])), [])}
        for status, pids in v.get("product_status", {}).items():
            for pid in pids:
                if pid in rels:                      # component-in-product: match BOTH sides
                    cat, comp, prod = rels[pid]
                    comp_p, prod_p = purls.get(comp), purls.get(prod)
                    hit = bool(comp_p and prod_p and purl_match(prod_p, parent) and in_sbom(comp_p))
                    target = f"{comp_p} {cat} {prod_p}"
                else:                                # standalone product
                    p = purls.get(pid)
                    hit = bool(p and (in_sbom(p) or purl_match(p, parent)))
                    target = p
                print(f"{v.get('cve')}\t{status}\t{flags.get(pid, '-')}\t{'MATCH' if hit else 'no match'}\t{target}")

if __name__ == "__main__":
    main(*sys.argv[1:3])

Test run

We ran it (python3 -I csaf_vex_join.py vex.json sbom.cdx.json) against the full example document and three small CycloneDX 1.6 SBOMs.

SBOM 1, image 4.2.1 (metadata.component.purl = pkg:oci/example-gateway@sha256%3A1111?tag=4.2.1), containing pkg:deb/debian/libexample@1.8.0-1?arch=amd64&distro=debian-12:

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
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

The SBOM’s extra arch and distro qualifiers did not block the match, because the VEX purl has none.

SBOM 2, image 4.3.0 with libexample 1.8.2: the results flip. The fixed statement matches and the known_not_affected one does not.

SBOM 3, the 4.2.1 SBOM again, but with the VEX component purl changed to ...libexample@1.8.0-1?arch=arm64: no match, because the VEX purl now requires a qualifier value the SBOM lacks.

What the script does not do: version ranges (product_version_range), CPE-only products, hashes, product_groups 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.

How Trivy applies CSAF VEX

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 --vex. Its matcher (pkg/vex/csaf.go) shows three things worth knowing:

• Only two statuses act. The status map holds known_not_affected and fixed. A match on either filters the finding. known_affected and under_investigation statements never change the result.
• Matching is by purl. If the detected package has no purl, or the vulnerability has no product_status, nothing is filtered.
• Relationship categories are not distinguished. The documentation says “the specified relationship category is not taken into account” and that default_component_of, installed_on and installed_with “are treated internally as depends_on”. 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. external_component_of and optional_component_of relationships are skipped. A status on a plain product ID, with no relationship, is matched against the package’s own purl, so it applies wherever that package appears.

So if a vendor’s CSAF file uses optional_component_of 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.

Common mistakes

• Matching the component alone. Covered above. It turns a statement about one product into a statement about all of them.
• Trusting known_not_affected with no impact statement. 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.
• Reading only branches. Products in full_product_names and relationships carry IDs too. A parser that only walks branches will report “unknown product” for most relationship-heavy files.
• Treating recommended as fixed. The spec allows recommending a version from the affected group.
• Ignoring tracking.version and current_release_date. VEX files are revised as investigations finish. Store the version you applied, and re-apply when it changes.

Where this fits

VEX is one input to a patch decision, not the decision. In our vulnerability prioritization workflow, 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 SBOM minimum elements guide covers which identifiers your SBOM should carry in the first place. Without purls in the SBOM, none of this matching works.

Limits of this article

We read CSAF 2.0 from the OASIS TC’s GitHub repository (the editor’s draft prose, headed “OASIS Standard, 18 November 2022”, 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’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.

Sources and verification

Scope. 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 1d1ab074, 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 VEX explainer covers what the statuses mean and how far to trust them; this article is only about moving statements between formats.

The short answer

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.

Of CycloneDX’s nine justifications, only code_not_present and code_not_reachable have a clear counterpart among the five CISA-derived labels that OpenVEX and CSAF share. Convert those two; carry the other seven as text.

Where VEX sits in a CycloneDX document

CycloneDX has no separate VEX document type. VEX is the vulnerabilities array of a BOM, and the fields that matter are:

• id: the vulnerability identifier, such as a CVE ID.
• affects[].ref: what the statement is about. The schema allows a bom-ref in the same document or a BOM-Link element. A BOM-Link has the form urn:cdx:serialNumber/version#bom-ref, and the schema’s pattern requires the serial number UUID, a version of 1 or more, and a fragment.
• analysis.state: one of resolved, resolved_with_pedigree, exploitable, in_triage, false_positive, not_affected.
• analysis.justification: one of nine reasons, described below.
• analysis.response: zero or more of can_not_fix, will_not_fix, update, rollback, workaround_available.
• analysis.detail: free text. The schema says that if a vulnerability is not exploitable, “this field should include specific details on why the component or service is not impacted.”

A VEX statement can sit inside the SBOM itself or in a separate BOM that only has vulnerabilities and refers back to the SBOM by BOM-Link. That second pattern matters for tooling, below.

States: four clean pairs and two lossy ones

The CycloneDX schema defines the six states in its meta:enum. Four map directly:

• not_affected: “The component or service is not affected by the vulnerability. Justification should be specified for all not_affected cases.” This is OpenVEX not_affected and CSAF known_not_affected.
• exploitable: “The vulnerability may be directly or indirectly exploitable.” This is OpenVEX affected and CSAF known_affected.
• in_triage: “The vulnerability is being investigated.” This is under_investigation in both.
• resolved: “The vulnerability has been remediated.” This is fixed in both.

Two lose meaning:

• false_positive: “The vulnerability is not specific to the component or service and was falsely identified or associated.” OpenVEX and CSAF have no status for “the scanner was wrong”. The safe target is not_affected, which is also what Trivy’s cdxStatus function does (case cdx.IASFalsePositive, cdx.IASNotAffected: return types.FindingStatusNotAffected). Keep the word false_positive in the impact statement so a reviewer can see it.
• resolved_with_pedigree: remediated “and evidence of the changes are provided in the affected components pedigree”. It becomes fixed, and the pointer to pedigree evidence is lost unless you keep it as text.

Justifications: two of nine line up

OpenVEX’s five justification labels come from CISA’s June 2022 status-justification document, and the CSAF 2.0 schema’s flags[].label 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.

Why so strict? The OpenVEX spec defines inline_mitigations_already_exist as built-in protections that “cannot be subverted by the attacker and cannot be configured or disabled by the user.” A CycloneDX protected_at_runtime or protected_by_compiler claim does not tell you that. protected_at_perimeter and protected_by_mitigating_control describe the deployment, not the product, and a mitigating control that “reduce[s] the likelihood and/or impact” is weaker than “not affected” in the CISA sense.

This mapping is our editorial reading of the published definitions. We did not find a mapping table published by the CycloneDX project or CISA.

OpenVEX gives you a way out: for not_affected, “a VEX statement MUST include either a status justification or an impact_statement.” So you can emit a not_affected statement with no label and an impact statement that preserves the original CycloneDX reason. CSAF’s VEX profile has the same escape hatch: each known_not_affected product needs either a machine-readable flag or a human-readable justification in threats with category impact.

Responses and action statements

For affected products, both targets require an action:

• OpenVEX: for affected, “a VEX statement MUST include a statement that SHOULD describe actions to remediate or mitigate the vulnerability” (action_statement).
• CSAF VEX profile: for known_affected, “additional product specific information SHALL be provided in /vulnerabilities[]/remediations as an action statement.”

CycloneDX’s response values give you a starting point. update and rollback fit CSAF’s vendor_fix remediation category, workaround_available fits workaround, and will_not_fix / can_not_fix fit no_fix_planned (or none_available), which the CSAF profile explicitly permits for an action statement. OpenVEX takes a free-text action_statement, so join the responses with analysis.detail. If an exploitable statement has neither a response nor detail, the converted statement will be valid but useless; send it back to the supplier.

BOM-Link: the part that silently drops statements

A CycloneDX VEX BOM that references components by BOM-Link is bound to one SBOM version. Trivy’s docs (v0.67) say the tool “only supports the Independent BOM and VEX BOM format, so you need to provide a separate VEX file alongside the SBOM,” that “BOM-Links must be placed in affects.ref,” and that the input SBOM must be CycloneDX. The usage example is trivy sbom trivy.sbom.cdx --vex trivy.vex.cdx. The feature is marked experimental.

Trivy’s code adds a detail the docs do not spell out: if the BOM-Link’s serial number or version does not equal the scanned SBOM’s, it logs URN doesn't match with SBOM 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.

OpenVEX has no BOM-Link. Products are identified by an @id such as a Package URL, so a converter has to resolve each BOM-Link to the referenced component’s purl in the SBOM. That is why the converter below takes both files.

A tested converter: CycloneDX VEX to OpenVEX

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 affects[].versions, services, or nested BOMs beyond components.

#!/usr/bin/env python3
"""Convert a CycloneDX VEX BOM (independent VEX, BOM-Link refs) to OpenVEX v0.2.0.
Usage: python3 cdx2openvex.py sbom.cdx.json vex.cdx.json author > out.openvex.json"""
import json, sys, hashlib
from datetime import datetime, timezone

STATUS = {  # CycloneDX analysis.state -> OpenVEX status
    "not_affected": "not_affected", "false_positive": "not_affected",
    "exploitable": "affected", "in_triage": "under_investigation",
    "resolved": "fixed", "resolved_with_pedigree": "fixed",
}
# Only the pairs whose definitions line up; everything else is carried as text.
JUSTIFICATION = {
    "code_not_present": "vulnerable_code_not_present",
    "code_not_reachable": "vulnerable_code_not_in_execute_path",
}

def purls_by_ref(sbom):
    serial, version = sbom["serialNumber"], sbom.get("version", 1)
    out, stack = {}, list(sbom.get("components", []))
    while stack:
        c = stack.pop()
        if "bom-ref" in c and "purl" in c:
            out[f"urn:cdx:{serial.removeprefix('urn:uuid:')}/{version}#{c['bom-ref']}"] = c["purl"]
        stack.extend(c.get("components", []))
    return out

def convert(sbom, vex, author):
    refs, statements, problems = purls_by_ref(sbom), [], []
    for v in vex.get("vulnerabilities", []):
        a = v.get("analysis", {})
        state = a.get("state")
        if state not in STATUS:
            problems.append(f"{v['id']}: no analysis.state, skipped"); continue
        products = []
        for af in v.get("affects", []):
            purl = refs.get(af["ref"])
            if purl: products.append({"@id": purl})
            else: problems.append(f"{v['id']}: {af['ref']} not found in SBOM")
        if not products: continue
        s = {"vulnerability": {"name": v["id"]}, "products": products, "status": STATUS[state]}
        detail = a.get("detail", "").strip()
        if s["status"] == "not_affected":
            j = JUSTIFICATION.get(a.get("justification"))
            if j: s["justification"] = j
            note = f"CycloneDX state={state}, justification={a.get('justification', 'none')}"
            s["impact_statement"] = f"{note}. {detail}".strip()
        elif s["status"] == "affected":
            resp = ", ".join(a.get("response", [])) or "none given"
            s["action_statement"] = f"CycloneDX response: {resp}. {detail}".strip()
        statements.append(s)
    body = json.dumps(statements, sort_keys=True).encode()
    doc = {"@context": "https://openvex.dev/ns/v0.2.0",
           "@id": "https://example.com/vex/" + hashlib.sha256(body).hexdigest()[:16],
           "author": author,
           "timestamp": datetime.now(timezone.utc).isoformat(timespec="seconds"),
           "version": 1, "statements": statements}
    return doc, problems

if __name__ == "__main__":
    sbom, vex = (json.load(open(p)) for p in sys.argv[1:3])
    doc, problems = convert(sbom, vex, sys.argv[3])
    json.dump(doc, sys.stdout, indent=2)
    for p in problems: print("WARN", p, file=sys.stderr)

Test run

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:

1. CVE-2021-44228 on log4j-core: not_affected, code_not_reachable.
2. CVE-2022-42003 on jackson-databind: not_affected, requires_configuration.
3. CVE-2022-1471 on snakeyaml: exploitable, response update.
4. CVE-2021-44228 again, but with a BOM-Link naming SBOM version 2 instead of 1.

Both input files passed check-jsonschema against the CycloneDX 1.6 schema. The run printed one warning to stderr and three statements; the output validated against openvex_json_schema.json (v0.2.0) with the Python jsonschema package:

WARN CVE-2021-44228: urn:cdx:3e671687-395b-41f5-a30f-a58921a69b79/2#pkg-log4j not found in SBOM

The statements array of the output:

[
{
  "vulnerability": { "name": "CVE-2021-44228" },
  "products": [ { "@id": "pkg:maven/org.apache.logging.log4j/log4j-core@2.14.1" } ],
  "status": "not_affected",
  "justification": "vulnerable_code_not_in_execute_path",
  "impact_statement": "CycloneDX state=not_affected, justification=code_not_reachable. JNDI lookups are never invoked; the app logs through SLF4J with Logback."
},
{
  "vulnerability": { "name": "CVE-2022-42003" },
  "products": [ { "@id": "pkg:maven/com.fasterxml.jackson.core/jackson-databind@2.13.0" } ],
  "status": "not_affected",
  "impact_statement": "CycloneDX state=not_affected, justification=requires_configuration. The deserialization feature this issue depends on is disabled in our ObjectMapper configuration."
},
{
  "vulnerability": { "name": "CVE-2022-1471" },
  "products": [ { "@id": "pkg:maven/org.yaml/snakeyaml@1.30" } ],
  "status": "affected",
  "action_statement": "CycloneDX response: update. Dependency upgrade ships in release 4.2."
}
]

The second statement is the important one: it stays not_affected 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.

Common mistakes

• Mapping every protected_* justification to inline_mitigations_already_exist. That label claims the protection cannot be disabled. A WAF rule or a compiler flag can.
• Dropping false_positive statements because the target format has no matching status. Map them to not_affected and say why.
• Dropping the detail text. It is often the only evidence a reviewer has, and both OpenVEX and CSAF have a place for it.
• Reusing a VEX BOM after regenerating the SBOM. BOM-Links name an exact serial number and version.
• Treating converted VEX as first-party. Keep the original author. OpenVEX author should be the organization that made the assessment, not the converter.

Where this fits

VEX is the “is my product actually affected” step in our vulnerability prioritization workflow, after the CVE record and before KEV, SSVC and EPSS. The SBOM that the VEX points at is covered in our guide to SBOM minimum elements in 2026. If you want a signal for which exploitable statements to fix first, our CVSS vs EPSS vs KEV comparison covers the trade-offs.

Limits of this article

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’s GitHub repository (schema and editor’s draft prose) rather than the OASIS-hosted standard. We read Trivy’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 affects needs a component reference the OpenVEX product may not resolve to.

Sources and verification