Multiple SAML libraries may incorrectly utilize the results of XML DOM traversal and canonicalization APIs in such a way that an attacker may be able to manipulate the SAML data without invalidating the cryptographic signature, allowing the attack to potentially bypass authentication to SAML service providers.
CWE-287: Improper Authentication
Security Assertion Markup Language (SAML) is an XML-based markup language for security assertions regarding authentication and permissions, most commonly used for single sign-on (SSO) services.
By modifying SAML content without invalidating the cryptographic signature, a remote, unauthenticated attacker may be able to bypass primary authentication for an affected SAML service provider.
Thanks to Kelby Ludwig of Duo Security for reporting this vulnerability.
This document was written by Garret Wassermann.