CVE-2026-9704: Red Hat Build Of Keycloak

High severity, CVSS 8.8. EPSS: 0.6% chance of exploitation in the next 30 days.

A flaw was found in Keycloak. An authenticated user with low privileges can exploit this vulnerability by sending an oversized subject_token JSON Web Token (JWT) to the TokenEndpoint. When the token exceeds a 4000-character limit, it is silently dropped, causing the system to fall back to client credentials. This allows the user to gain the permissions of the client's service account, leading to privilege escalation.

Affected products

• Red Hat Build Of Keycloak: affected versions not specified

Published 2026-05-27. Last modified 2026-06-26.