Keycloak's ClientRegistrationAuth component throws an ArrayIndexOutOfBoundsException when a client registration endpoint receives a malformed "Authorization: Bearer" header. The resulting HTTP 500 response can repeatedly crash the service, effectively denying legitimate requests. This flaw is a classic example of CWE‑125, where unchecked array bounds lead to application failure. The impact is a denial of service to all users relying on the affected Keycloak service.

The vulnerability affects Red Hat Build of Keycloak. No specific version numbers were listed in the advisory; therefore any deployment of Red Hat's Keycloak build that has not been patched may be at risk. The vendor name is Red Hat and the product is their build of Keycloak.

The CVSS score of 5.3 indicates moderate severity. EPSS is not available, and KEV does not list this CVE, so widespread exploitation has not yet been observed. The attack can be performed remotely and unauthenticated; an attacker simply sends a crafted POST request to a client registration endpoint with the malformed header. Because only a standard HTTP request is required, exploitation is straightforward for anyone with network access to the service. The resulting denial can affect availability for all clients using that Keycloak instance.