Ruby-saml has a SAML authentication bypass due to namespace 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 0.0042, the 36th percentile, on 5 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 8 Dec 2025. New records show when each source confirmed them.

Sources

• GitHub Advisory Database: GHSA-9v8j-x534-2fx3
• OSV: GHSA-9v8j-x534-2fx3
• github.com/SAML-Toolkits/ruby-saml/security/advisories/GHSA-9v8j-x534-2fx3
• nvd.nist.gov/vuln/detail/CVE-2025-66567
• github.com/SAML-Toolkits/ruby-saml/commit/e9c1cdbd0f9afa467b585de279db0cbd0fb8ae97
• github.com/SAML-Toolkits/ruby-saml
• github.com/advisories/GHSA-754f-8gm6-c4r2
• github.com/rubysec/ruby-advisory-db/blob/master/gems/ruby-saml/CVE-2025-66567.yml

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.