[ CVE-2026-11800 · Published 25 Jun 2026 ]
Keycloak has authentication bypass via jwt algorithm confusion
CVSS 8.1
EPSS <1%Fix available
[ Description ]Official 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.
[ Fixes ]Fixes and patches
- org.keycloak:keycloak-services 26.6.4Fixed version · GitHub Advisories · maven package org.keycloak:keycloak-services: upgrade to 26.6.4 or later (affected < 26.6.4)
[ Packages ]Affected open-source packages
- org.keycloak:keycloak-services mavenAffected < 26.6.4 · fixed in 26.6.4 · GHSA-j97h-3f8r-mrjr
[ References ]References
- access.redhat.com/errata/RHSA-2026:30083vendor-advisoryx_refsource_REDHAT
- access.redhat.com/errata/RHSA-2026:30084vendor-advisoryx_refsource_REDHAT
- access.redhat.com/security/cve/CVE-2026-11800vdb-entryx_refsource_REDHAT
- bugzilla.redhat.com/show_bug.cgiissue-trackingx_refsource_REDHAT