SimpleSAMLphp SP accepts a response from an unexpected IdP when unsigned `Response/InResponseTo` is combined with a signed assertion lacking `SubjectConfirmationData/InResponseTo`

Summary SimpleSAMLphp's SAML SP ACS path does not enforce the IdP selected for an SP-initiated login. If a saved SP state contains ExpectedIssuer = IdP A, but the ACS receives a valid response from IdP B, the code logs a warning and continues processing instead of rejecting the response. That...

PT-2026-55453

Name of the Vulnerable Software and Affected Versions SimpleSAMLphp versions prior to 1.18.6 SimpleSAMLphp versions prior to 2.4.7 SimpleSAMLphp versions prior to 2.5.2 Description The SAML SP ACS path fails to enforce the Identity Provider IdP selected during an SP-initiated login. When a saved ...