CVE-2025-66567: Onelogin Ruby-SAML

Critical severity, CVSS 9.1. EPSS: 0.4% chance of exploitation in the next 30 days.

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.

Affected products

• Onelogin Ruby-SAML: before 1.18.0 (fixed in 1.18.0)

Published 2025-12-09. Last modified 2026-06-17.