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GHSA-9rjg-x2p2-h68h
No affected components available
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 is_a 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< 4.1.30api-platform/core>= 4.2.0, < 4.2.26api-platform/core>= 4.3.0, < 4.3.12
Older major series (2.x, 3.x) ship the same vulnerable code path and are end-of-life; no fix is planned.
Patched versions
4.1.304.2.264.3.12
Fix
An is_a guard is added inside AbstractItemNormalizer::getResourceFromIri() (and the equivalent inline call sites on 4.1) so that a mismatched IRI throws InvalidArgumentException, mirroring the operation-aware check the IriConverter already performs when an operation is supplied. This forces a 400 Bad Request response for cross-type IRIs instead of a silent assignment.
Workarounds
Declare a PHP type on every writable relation property (e.g. public ?Foo $relation = null; instead of @var Foo $relation). Symfony's PropertyAccessor will then reject a mismatched object with InvalidTypeException. This does not cover collections of mixed-type interfaces; upgrading to a patched version is the only complete fix.
Proof of concept
A functional test posts a Bar IRI to a Foo-declared relation on an untyped property. Without the fix the server responds with HTTP 201 and the Bar IRI appears in the response payload. With the fix the server responds with HTTP 400 (Invalid IRI "/bars/1").
Full PoC: tests/Functional/Security/TypeConfusionRelationIriTest.php in the patched branches.
References
src/Serializer/AbstractItemNormalizer.php— vulnerable relation IRI loadsrc/Symfony/Routing/IriConverter.php— conditionalis_aguard (operation-aware path)
Credit
Reported by @alexandre-daubois.
The vulnerability can be exploited over the network without needing physical access. It is easy for an attacker to exploit this vulnerability. An attacker needs basic access or low-level privileges. No user interaction is needed for the attacker to exploit this vulnerability. The impact is confined to the system where the vulnerability exists. There is a high impact on the integrity of the data.
Exploitation attempts have been detected. Elevated vigilance and prompt remediation are advised.
The exploit probability is very low. The vulnerability is unlikely to be exploited in the next 30 days.
We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.
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