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

Source: https://junglewise.ai/threats/cve-2025-66567-ruby-saml-has-a-saml-authentication-bypass-due-to-namespace  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2025-12-09  
License: CC BY 4.0 with a link back

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](https://junglewise.ai/threats/technologies/ruby-saml), [ruby-saml (RubyGems)](https://junglewise.ai/threats/technologies/rubygems-ruby-saml). Vendors: [Onelogin](https://junglewise.ai/threats/vendors/onelogin), [RubyGems](https://junglewise.ai/threats/vendors/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

  ```sh
  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

## Related threats

- [Ruby-saml allows a Libxml2 Canonicalization error to bypass Digest/Signature validation](https://junglewise.ai/threats/cve-2025-66568-ruby-saml-allows-a-libxml2-canonicalization-error-to-bypass)
- [Ruby SAML DOS vulnerability with large SAML response](https://junglewise.ai/threats/cve-2025-54572-ruby-saml-dos-vulnerability-with-large-saml-response)
- [Ruby SAML allows a SAML authentication bypass due to namespace handling (parser differential)](https://junglewise.ai/threats/cve-2025-25292-ruby-saml-allows-a-saml-authentication-bypass-due-to-namespace)
- [Ruby SAML allows a SAML authentication bypass due to DOCTYPE handling (parser differential)](https://junglewise.ai/threats/cve-2025-25291-ruby-saml-allows-a-saml-authentication-bypass-due-to-doctype)
- [Ruby SAML allows remote Denial of Service (DoS) with compressed SAML responses](https://junglewise.ai/threats/cve-2025-25293-ruby-saml-allows-remote-denial-of-service-dos-with-compressed)