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GHSA-j97h-3f8r-mrjr

Keycloak has authentication bypass via jwt algorithm confusion

Source: GitHub Advisory Database (reviewed) High CVE-2026-11800

Packages

EcosystemPackageAffectedFixed in
Maven org.keycloak:keycloak-services < 26.6.4 26.6.4

Details

As written in the advisory (Markdown source, shown as plain text).

### 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.

References

External links from the advisory. They lead to third-party sites.