Executive brief
Keycloak, an identity and access management platform used for authentication and authorization, accepts RFC-compliant matrix parameters in URLs that reverse proxies may mishandle. An attacker can exploit this to bypass security filters intended to block access to sensitive administrative endpoints, potentially gaining exposure to restricted functionality that operators believed was protected.
Technical details
This improper input validation vulnerability stems from Keycloak accepting matrix parameters (semicolon-delimited parameters in URL path segments) that comply with RFC specifications. However, many reverse proxy configurations do not correctly parse or filter these parameters, allowing an attacker to craft requests that mask sensitive path segments and evade proxy-level access controls. The vulnerability requires network access to a Keycloak instance deployed behind a vulnerable reverse proxy configuration; no authentication is required. An attacker can bypass path-based filtering to reach administrative or sensitive endpoints, potentially gaining unauthorized access to restricted functionality. Patched versions are available from the vendor.
Affected products
- Red Hat Keycloak
Timeline
- 2026-01-15: disclosed