Medium [CVE-2026-18573] Client access-type policy condition bypass during client update

A flaw was found in the keycloak-services component of Keycloak, which is used for managing authentication and authorization flows. The issue occurs when a realm administrator configures client policies to enforce specific authentication requirements on confidential clients.

Due to improper evaluation of the client state during an update operation, an attacker with client management permissions can bypass these security policies by first creating a public client and then updating it to a confidential client with weaker authentication.

This can result in the persistence of clients that do not comply with the intended security hardening of the realm. The Red Hat Product Security team has assessed the severity of this vulnerability as Moderate, given that exploitation requires existing client management privileges or a dynamic registration token.

Successful exploitation allows an attacker to bypass realm-specific client policy conditions and persist confidential clients with weaker authentication than required by policy. The vulnerability's root cause is the evaluation of update operations against the previous client state rather than the proposed new state.

Weakness: CWE-862. Affected Red Hat products: Red Hat build of Keycloak 26.6; Red Hat build of Keycloak 26.6.7.