Impact

Given a valid SAML Response, it may be possible for an attacker to mutate the XML document in such a way that gosaml2 will trust a different portion of the document than was signed.

Depending on the implementation of the Service Provider this enables a variety of attacks, including users accessing accounts other than the one to which they authenticated in the Identity Provider, or full authentication bypass.

Patches

Service Providers utilizing gosaml2 should upgrade to v0.6.0 or greater.

References

• GHSA-xhqq-x44f-9fgg
• https://nvd.nist.gov/vuln/detail/CVE-2020-29509
• https://github.com/mattermost/xml-roundtrip-validator/blob/master/advisories/unstable-attributes.md
• https://security.netapp.com/advisory/ntap-20210129-0006/
• russellhaering/gosaml2@42606da
• https://pkg.go.dev/vuln/GO-2021-0060