Keycloak-services: keycloak-services: inactive out-of-audience token introspection leaks signed jwt claim

A flaw was found in the OIDC token introspection endpoint of the keycloak-services component. Keycloak is an open-source identity and access management solution used to secure modern applications and services.

The issue occurs when a confidential client, configured to receive signed JWT introspection responses, attempts to introspect a token issued for a different audience. Although the endpoint correctly identifies the token as inactive for that client, it still returns the full set of token claims within a signed JWT field.

This allows an unauthorized client to bypass audience-based restrictions and access sensitive information contained in the token.

Affected product named by the advisory: Red Hat Build of Keycloak.