A flaw was found in the secure-redirect-uris-enforcer client policy of Keycloak, an identity and access management solution. The issue occurs when the policy is configured to allow loopback addresses, as Keycloak resolves hostnames via DNS during validation. An attacker can bypass domain allowlist restrictions by using a hostname that resolves to a loopback address, potentially allowing the registration of unauthorized redirect URIs.
Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability.