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Medium, CVSS 6.5amended

API Platform Core: Relation IRIs are not type-checked: a related resource can be denormalised as the wrong resource type (type confusion)

CVE-2026-54164GHSA-9rjg-x2p2-h68h

What to do

Vendor fix available. Upgrade each affected package to the fixed version on its release line (api-platform/core 4.3.12, 4.2.26, 4.1.30), redeploy, then verify what is actually installed.

This page has no inventory attached, so it cannot say whether you are affected. A vendor fix is not proof that your deployment is fixed.

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Affected packages

  • Packagist api-platform/core

    Affected
    < 4.1.30>= 4.2.0, < 4.2.26>= 4.3.0, < 4.3.12
    Fixed in
    4.1.30, 4.3.12, 4.2.26

Sources

Severity and exploitation
Exploitation
No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.
CVSS
6.5 · CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N
EPSS
  • CVE-2026-54164: 0.34% estimated exploitation activity in the next 30 days; percentile 27.01 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.
Source description

As published by the source; long descriptions are shortened.

Summary The API Platform serializer's AbstractItemNormalizer does not validate the resource type returned when resolving relation IRIs, allowing type confusion where a resource of an unintended type can be silently assigned to a relation property. Impact An attacker who can submit write requests (POST/PUT/PATCH) to an API Platform endpoint with writable relations can supply a relation IRI pointing to a resource of a different type than the relation's declared class. Because getResourceFromIri() does not pass an $operation to IriConverter::getResourceFromIri(), the isa type guard at IriConverter.php:86 is skipped. For untyped relation properties (legacy @var-only style), the wrong-typed object is silently assigned, corrupting invariants and potentially feeding downstream logic that assumes the declared type (CWE-843). For typed properties (modern PHP 8.x), the substitution is blocked by Symfony's PropertyAccessor with an InvalidTypeException. Affected versions - api-platform/core <…

Dates and revisions
Published by the source
Last modified by the source
Source last checked
  1. Revision 2 · amended ·

    Amended from ghsa record GHSA-9rjg-x2p2-h68h

  2. Revision 1 · created ·

    Published from osv record GHSA-9rjg-x2p2-h68h

Agent brief

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# Patch Next advisory brief: CVE-2026-54164

Advisory: API Platform Core: Relation IRIs are not type-checked: a related resource can be denormalised as the wrong resource type (type confusion)
IDs: CVE-2026-54164, GHSA-9rjg-x2p2-h68h
Record: https://patchnext.com/advisories/cve-2026-54164 (revision 2, source checked 26 Oct 2026, 14:50 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 6.5)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: api-platform/core 4.3.12, 4.2.26, 4.1.30. A vendor fix does not mean a deployment is fixed.

## Affected components
- Packagist api-platform/core: affected < 4.1.30; >= 4.2.0, < 4.2.26; >= 4.3.0, < 4.3.12; fixed in 4.1.30, 4.3.12, 4.2.26

## Suggested inspection (read-only)
- Packagist api-platform/core: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on api-platform/core.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-9rjg-x2p2-h68h (OSV record GHSA-9rjg-x2p2-h68h lists affected ranges: Packagist api-platform/core >=0 =4.2.0 =4.3.0 <4.3.12 (fixed))
- Verified: https://github.com/advisories/GHSA-9rjg-x2p2-h68h (GitHub-reviewed advisory GHSA-9rjg-x2p2-h68h lists affected ranges: Packagist api-platform/core >=0 =4.2.0 =4.3.0 <4.3.12)

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