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CVE-2025-66567 — ruby-saml

Fix: SAML-Toolkits/ruby-saml@e9c1cdb

CVE-2025-66567 is a CWE-347 vulnerability in ruby-saml. A fix is available for ruby-saml — see the affected versions and patch details below.

ruby-saml has a SAML authentication bypass due to namespace handling (parser differential)

Also known asGHSA-9v8j-x534-2fx3
Published
Updated
Affected
1 pkg
Patched
1 / 1
Exploits
None indexed
Exploitation data as of Nov 6, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

  • CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
  • A successful exploit gives an attacker total control of the affected component, not partial access.
  • CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for CVE-2025-66567.

EPSS Exploitation Probability

via FIRST.org ↗
0.4%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs36th percentile — riskier than 36% of all scored CVEsHighest risk
0.00%0.31%0.61%0.92%0.1%0.4%May 26Sep 26Nov 26

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

Real-World Exposure

1 pkg affected
💎ruby-saml

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects RubyGems packages — download data is not available via public APIs for these ecosystems.

Description

Summary

Ruby-saml up to and including 1.12.4, there is an authentication bypass vulnerability because of an incomplete fix for CVE-2025-25292. ReXML and Nokogiri parse XML differently, the parsers can generate entirely different document structures from the same XML input. That allows an attacker to be able to execute a Signature Wrapping attack. The vulnerability does not affect the version 1.18.0.

Impact

That allows an attacker to be able to execute a Signature Wrapping attack and bypass the authentication

Affected Packages

1 total 1 fixed
EcosystemPackageVulnerable rangeFix
💎RubyGemsruby-samlall versions1.18.0bundle update ruby-saml --conservative

Affected Products

1 product · 1 configurations
Application
ruby-samlonelogin
< 1.18.0
range

Detection & mitigation playbook

Open-source dependency

  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for ruby-saml, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Fix

    Update ruby-saml to 1.18.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2025-66567 is resolved across your whole dependency graph.

  3. Workarounds

    Put an independent control in front of the weakness: restrict the affected endpoint or interface to trusted networks, require an additional authentication factor or proxy-level check, and invalidate existing sessions and credentials in case the flaw has already been used.

Frequently Asked Questions

### Summary Ruby-saml up to and including 1.12.4, there is an authentication bypass vulnerability because of an incomplete fix for CVE-2025-25292. ReXML and Nokogiri parse XML differently, the parsers can generate entirely different document structures from the same XML input. That allows an attacker to be able to execute a Signature Wrapping attack. The vulnerability does not affect the version 1.18.0. ### Impact That allows an attacker to be able to execute a Signature Wrapping attack and bypass the authentication
O3 Security · Impact-Aware SCA

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CVE-2025-66567: ruby-saml Auth Bypass — Fixed in 1.18.0