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GHSA-29fc-p6c4-24cg

MediumCVSS 4.9 / 10
Published May 27, 2026·Last modified May 27, 2026
Affected Components(0)

No affected components available

Description

Description

OidcTokenHandler is Symfony's built-in access-token handler for OpenID Connect: it validates a bearer JWT and returns the authenticated user identity. It delegates claim validation to the web-token/jwt-checker library's ClaimCheckerManager.

OidcTokenHandler::verifyClaims() registers audience (aud), issuer (iss), and expiry (exp) checkers, but never passes the $mandatoryClaims argument to ClaimCheckerManager::check(). That method only validates claims that are present in the token: a checker for an absent claim is silently skipped. A validly-signed JWT that simply omits aud, iss, and exp therefore passes verification.

Resolution

The OidcTokenHandler now calls the ClaimCheckerManager with the list of mandatory claims so that tokens missing aud, iss, or exp are rejected.

The patch for this issue is available here for branch 6.4.

Credits

Symfony would like to thank Claude Mythos Preview (via Project Glasswing) for reporting the issue and providing the fix.

Risk Scores
Base Score
4.9

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.

Threat Intelligence
4.9

Exploitation attempts have been detected. Elevated vigilance and prompt remediation are advised.

EPSS
0.24%

The exploit probability is very low. The vulnerability is unlikely to be exploited in the next 30 days.

Exploit
Not available

We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.

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