Keycloak's missing timestamp validation allows attackers to extend SAML response validity periods

A flaw was found in Keycloak's SAML brokering functionality. When Keycloak is configured as a client in a Security Assertion Markup Language (SAML) setup, it fails to validate the NotOnOrAfter timestamp within the SubjectConfirmationData. This allows an attacker to delay the expiration of SAML responses, potentially extending the time a response is considered valid and leading to unexpected session durations or resource consumption.