CVE-2025-66567: Ruby-saml has a SAML authentication bypass due to namespace handling (parser differential)

CVE-2025-66567 · Severity: critical · CVSS 9.1 · Published 2025-12-09

The ruby-saml library is for implementing the client side of a SAML authorization. ruby-saml versions up to and including 1.12.4 contain an authentication bypass vulnerability due to an incomplete fix for CVE-2025-25292. ReXML and Nokogiri parse XML differently, generating entirely different document structures from the same input. This allows an attacker to execute a Signature Wrapping attack. This issue is fixed in version 1.18.0.

Technologies: Onelogin Ruby-Saml, ruby-saml (RubyGems). Vendors: Onelogin, RubyGems.

Quick answers

Is CVE-2025-66567 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2025-66567 being exploited in the wild.
How severe is CVE-2025-66567?
Critical severity, with a CVSS score of 9.1, published 9 December 2025.
Which products and versions are affected?
ruby-saml (RubyGems) ECOSYSTEM:introduced=0,fixed=1.18.0.
Is there a fix for CVE-2025-66567?
Yes. ruby-saml (RubyGems): upgrade to 1.18.0 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
Am I affected by CVE-2025-66567?
Check whether you run Onelogin Ruby-Saml or ruby-saml (RubyGems) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

How to fix

  • ruby-saml (RubyGems): upgrade to 1.18.0 or later
    bundle update ruby-saml

Affected products

  • Onelogin Ruby-Saml
  • ruby-saml (RubyGems) ECOSYSTEM:introduced=0,fixed=1.18.0

Identifiers

  • CVE-2025-66567
  • GHSA-9v8j-x534-2fx3

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