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

How the Mentioned CVE Works:

The CVE-2025-XXXX vulnerability in Ruby SAML arises due to inconsistent XML namespace handling between the ReXML and Nokogiri parsers. When processing SAML responses, these parsers interpret XML namespaces differently, leading to divergent document structures from the same input. This discrepancy enables an attacker to craft a malicious SAML response that exploits the parser differential, effectively bypassing signature validation. By manipulating the XML structure, the attacker can execute a Signature Wrapping attack, where the SAML response appears valid to the application but contains unauthorized assertions. This allows the attacker to impersonate a legitimate user, leading to authentication bypass and unauthorized access to protected resources.

DailyCVE Form:

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

What Undercode Say:

Exploitation:

1. Craft Malicious SAML Response:

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

  <saml:Response xmlns:saml="urn:oasis:names:tc:SAML:2.0:assertion">
  <saml:Assertion>
  <!-- Malicious content -->
  </saml:Assertion>
  </saml:Response>
  

2. Signature Wrapping:

• Exploit the parser differential to wrap the signature around unauthorized assertions.
• Example:

  python3 saml_wrapper.py -i legit_response.xml -o malicious_response.xml
  

3. Send to Target:

• Submit the crafted SAML response to the target application.
• Example:

  curl -X POST -d @malicious_response.xml https://target.com/saml/acs
  

Protection:

1. Update Ruby SAML:

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

  gem update ruby-saml
  

2. Validate XML Parsing:

• Ensure consistent XML parsing by standardizing on a single parser (e.g., Nokogiri).
• Example:

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

3. Signature Verification:

• Implement strict signature validation to detect tampering.
• Example:

  settings = OneLogin::RubySaml::Settings.new
  settings.soft = false Enforce strict validation
  

4. Namespace Normalization:

• Normalize XML namespaces before processing.
• Example:

  doc.remove_namespaces!
  

5. Monitor Logs:

• Monitor SAML authentication logs for unusual activity.
• Command:

  tail -f /var/log/saml_auth.log
  

6. Security Testing:

• Use tools like `Burp Suite` or `OWASP ZAP` to test for XML vulnerabilities.
• Example:

  zap-cli active-scan -r https://target.com/saml/acs
  

  By following these steps, organizations can mitigate the risk of authentication bypass and secure their SAML implementations.

References:

Reported By: https://github.com/advisories/GHSA-754f-8gm6-c4r2
Extra Source Hub:
Undercode

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