Affected: keycloak, Red Hat build of Keycloak 24, Red Hat build of Keycloak 24.0.9, Red Hat build of Keycloak 26.0, Red Hat build of Keycloak 26.0.6, Red Hat Build of Keycloak, Red Hat JBoss Enterprise Application Platform 8

A vulnerability was found in the Keycloak Server. The Keycloak Server is vulnerable to a denial of service (DoS) attack due to improper handling of proxy headers. When Keycloak is configured to accept incoming proxy headers, it may accept non-IP values, such as obfuscated identifiers, without proper validation. This issue can lead to costly DNS resolution operations, which an attacker could exploit to tie up IO threads and potentially cause a denial of service. The attacker must have access to send requests to a Keycloak instance that is configured to accept proxy headers, specifically when reverse proxies do not overwrite incoming headers, and Keycloak is configured to trust these headers.