GitHub Advisoryadvisory · Maven
GHSA-j97h-3f8r-mrjr Keycloak has authentication bypass via jwt algorithm confusion
HIGH
Official page ↗
- Aliases
- CVE-2026-11800
- Ecosystem
- Maven
- Packages
- org.keycloak:keycloak-services
- Severity
- High
- CVSS vector
- CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N
- Weaknesses
- CWE-347
- Reviewed
- 2026-11-03
Affected packages
• Maven org.keycloak:keycloak-services: < 26.6.4 → fixed in 26.6.4
Description
Description
A flaw was found in Keycloak. This JWT algorithm confusion vulnerability in the JWT Authorization Grant flow allows an attacker with valid client credentials to bypass signature verification. By forging an assertion, the attacker can create unauthorized access tokens. This enables the attacker to impersonate any federated user linked to the affected Identity Provider, leading to unauthorized access and potential privilege escalation.
Related
Alias · CVE (1)
- CVE-2026-11800 A flaw was found in Keycloak. vulnerability
Weakness · CWE (1)
- CWE-347 Improper Verification of Cryptographic Signature weakness
References
- https://github.com/keycloak/keycloak/security/advisories/GHSA-j97h-3f8r-mrjr web
- https://nvd.nist.gov/vuln/detail/CVE-2026-11800 advisory
- https://github.com/keycloak/keycloak/issues/50357 web
- https://github.com/keycloak/keycloak/pull/50374 web
- https://github.com/keycloak/keycloak/commit/6d61885f20ac59a2ff8b823fc9ed1f1ef1019951 web
- https://github.com/keycloak/keycloak/commit/d343c7373dcc7bfeb9dc14de2309836299c81837 web
- https://access.redhat.com/errata/RHSA-2026:30083 web
- https://access.redhat.com/errata/RHSA-2026:30084 web
- https://access.redhat.com/security/cve/CVE-2026-11800 web
- https://bugzilla.redhat.com/show_bug.cgi?id=2487006 web
- https://github.com/keycloak/keycloak package
- https://github.com/keycloak/keycloak/releases/tag/26.6.4 web
- https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-11800.json web