Ruby SAML, Authentication Bypass, CVE-2025-XXXX (High)

How the Mentioned CVE Works:

The CVE-2025-XXXX vulnerability in Ruby SAML arises due to differences in XML parsing between ReXML and Nokogiri libraries. SAML (Security Assertion Markup Language) relies on XML for authentication and authorization data. When processing SAML responses, Ruby SAML uses these parsers to validate XML signatures. However, the parsers interpret the same XML input differently, leading to discrepancies in the document structure. An attacker can exploit this by crafting a malicious SAML response with a manipulated XML structure, such as a Signature Wrapping attack. This allows the attacker to bypass authentication by tricking the system into accepting an invalid or unauthorized SAML assertion as valid.

DailyCVE Form:

Platform: Ruby SAML
Version: < 1.12.4, >= 1.13.0, < 1.18.0
Vulnerability: Authentication Bypass
Severity: High
Date: Mar 12, 2025

What Undercode Say:

Exploitation:

1. Craft Malicious SAML Response:

• Use tools like `xmllint` or `xmlstarlet` to manipulate XML structures.
• Example:

  <saml:Assertion>
  <ds:Signature>...</ds:Signature>
  <saml:Subject>...</saml:Subject>
  <saml:Conditions>...</saml:Conditions>
  </saml:Assertion>
  

• Insert additional XML elements to confuse parsers.

2. Signature Wrapping:

• Exploit parser differences to wrap the signature around unauthorized data.
• Example:

  <saml:Assertion>
  <ds:Signature>...</ds:Signature>
  <saml:Subject>...</saml:Subject>
  <saml:Conditions>...</saml:Conditions>
  <saml:UnauthorizedData>...</saml:UnauthorizedData>
  </saml:Assertion>
  

3. Send to Target:

• Use tools like `curl` or custom scripts to send the crafted SAML response to the target application.
• Example:

  curl -X POST -d @malicious_saml.xml https://target.com/saml/consume
  

Protection:

1. Update Ruby SAML:

• Upgrade to patched versions: 1.12.4 or 1.18.0.
• Command:

  gem update ruby-saml
  

2. Validate XML Strictly:

• Implement strict XML validation to ensure consistent parsing.
• Example:

  require 'ruby-saml'
  settings = OneLogin::RubySaml::Settings.new
  settings.soft = false Disable soft validation
  

3. Use a Single Parser:

• Standardize on a single XML parser (e.g., Nokogiri) to avoid parser differentials.
• Example:

  require 'nokogiri'
  doc = Nokogiri::XML(saml_response)
  

4. Monitor Logs:

• Check for unusual SAML responses or authentication attempts.
• Example:

  tail -f /var/log/saml.log
  

5. Implement Signature Verification:

• Ensure all SAML responses are properly signed and verified.
• Example:

  response = OneLogin::RubySaml::Response.new(saml_response)
  response.settings = settings
  response.is_valid?
  

  By following these steps, you can mitigate the risk of authentication bypass and secure your Ruby SAML implementation.

References:

Reported By: https://github.com/advisories/GHSA-4vc4-m8qh-g8jm
Extra Source Hub:
Undercode

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