CoreWCF: SamlSerializer skips SignatureValue verification when SAML signing token is not an X.509 certificate

Impact

When a service is configured to validate SAML tokens using a method other than X.509 certificate signing, the final signature verification is skipped.

Preconditions

The service is configured to authenticate using SAML tokens and an out of band token resolver (commonly the IssuerTokenResolver of IssuedTokenServiceCredential) holds a non-X.509 SecurityToken whose key identifier the attacker can reference in the assertion’s <KeyInfo> - for example a BinarySecretSecurityToken representing the symmetric proof key issued by a WS-Trust symmetric-key holder-of-key STS.

Patches

Fixed in CoreWCF v1.8.1 and v1.9.1

Workarounds

None