Summary
A flaw was found in the protocol mapper and identity resolution components of Keycloak. The issue occurs when a client manager uses hardcoded-claim mappers to override identity claims in sessionless service-account tokens. Because these tokens lack a session ID, Keycloak may incorrectly resolve the token bearer as a different, highly privileged user based on the manipulated claims. This can allow an attacker with limited client management permissions to impersonate a realm administrator and gain full control over the realm.