CVE-2026-4634: Red Hat Build Of Keycloak

High severity, CVSS 7.5. EPSS: 0.9% chance of exploitation in the next 30 days.

A flaw was found in Keycloak. An unauthenticated attacker can exploit this vulnerability by sending a specially crafted POST request with an excessively long scope parameter to the OpenID Connect (OIDC) token endpoint. This leads to high resource consumption and prolonged processing times, ultimately resulting in a Denial of Service (DoS) for the Keycloak server.

Affected products

• Red Hat Build Of Keycloak: affected versions not specified; version 26.2 only; version 26.2.15 only; version 26.4 only; version 26.4.11 only

Published 2026-04-02. Last modified 2026-10-06.