A flaw was found in Keycloak's Client Policies, specifically within the `org.keycloak.protocol.oidc` component. When certain condition providers (client-type, client-roles, client-attributes, client-scopes) are used to enforce security restrictions, the `reject-ropc-grant` executor is silently bypassed. This allows an unauthenticated remote attacker to obtain tokens via a Resource Owner Password Credentials (ROPC) grant, even when a policy is explicitly configured to block it. This bypass can lead to unauthorized access and information disclosure.
Credits
Red Hat would like to thank Evan Hendra (Independent Security Researcher) for reporting this issue.
