CVE-2026-11800: Red Hat Build Of Keycloak

High severity, CVSS 8.1. EPSS: 0.3% chance of exploitation in the next 30 days.

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.

Affected products

• Red Hat Build Of Keycloak: from 26.6, before 26.6.4 (fixed in 26.6.4)

Published 2026-06-25. Last modified 2026-07-15.