CVE-2026-11800
HighCVSS 8.1Exploitation Probability (EPSS)
Low risk8th percentile — higher than 8% of all known CVEs
Summary
A flaw was found in Keycloak where JWT algorithm confusion 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 and impersonate any federated user linked to the affected Identity Provider.
Risk Assessment
The risk includes unauthorized access and potential privilege escalation, which could lead to account takeover and data breach.
Recommendation
Immediately update Keycloak to a patched version. Additionally, review the JWT Authorization Grant flow configuration and consider restricting trusted signature algorithms.
Original NVD description (English source)
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.