The PKIX trust engines in Shibboleth Identity Provider before 2.4.4 and OpenSAML Java (OpenSAML-J) before 2.6.5 trust candidate X.509 credentials when no trusted names are available for the entityID, which allows remote attackers to impersonate an entity via a certificate issued by a shibmd:KeyAuthority trust anchor.
Shibboleth OpenSAML library 2.4.x before 2.4.3 and 2.5.x before 2.5.1, and IdP before 2.3.2, allows remote attackers to forge messages and bypass authentication via an "XML Signature wrapping attack."
The (1) BasicParserPool, (2) StaticBasicParserPool, (3) XML Decrypter, and (4) SAML Decrypter in Shibboleth OpenSAML-Java before 2.6.1 set the expandEntityReferences property to true, which allows remote attackers to conduct XML external entity (XXE) attacks via a crafted XML DOCTYPE declaration.
The (1) HttpResource and (2) FileBackedHttpResource implementations in OpenSAML do not verify that the server hostname matches a domain name in the subject's Common Name (CN) or subjectAltName field of the X.509 certificate, which allows man-in-the-middle attackers to spoof SSL servers via an arbitrary valid certificate.