Ruby SAML allows a SAML authentication bypass due to DOCTYPE handling (parser differential)

Not analysed yet

We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.

Severity and exploitation

• CISA KEV Not listed.
• EPSS 0.21, the 97th percentile, on 6 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

Timeline

This record came from the full history of the GitHub Advisory Database, published 12 Mar 2025. New records show when each source confirmed them.

Sources

• GitHub Advisory Database: GHSA-4vc4-m8qh-g8jm
• OSV: GHSA-4vc4-m8qh-g8jm
• github.com/SAML-Toolkits/ruby-saml/security/advisories/GHSA-4vc4-m8qh-g8jm
• github.com/omniauth/omniauth-saml/security/advisories/GHSA-hw46-3hmr-x9xv
• nvd.nist.gov/vuln/detail/CVE-2025-25291
• github.com/SAML-Toolkits/ruby-saml/commit/e76c5b36bac40aedbf1ba7ffaaf495be63328cd9
• github.com/SAML-Toolkits/ruby-saml/commit/e9c1cdbd0f9afa467b585de279db0cbd0fb8ae97
• about.gitlab.com/releases/2025/03/12/patch-release-gitlab-17-9-2-released
• github.blog/security/sign-in-as-anyone-bypassing-saml-sso-authentication-with-parser-differentials
• github.com/SAML-Toolkits/ruby-saml
• github.com/SAML-Toolkits/ruby-saml/releases/tag/v1.12.4
• github.com/SAML-Toolkits/ruby-saml/releases/tag/v1.18.0
• github.com/rubysec/ruby-advisory-db/blob/master/gems/ruby-saml/CVE-2025-25291.yml
• lists.debian.org/debian-lts-announce/2025/04/msg00011.html

Facts on this page come from the GitHub Advisory Database (CC-BY 4.0), OSV and the other sources listed, as published. We don’t reproduce full advisory descriptions, which can contain exploit code.