CVE-2025-66567 CRITICAL

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

Vendor Saml-Toolkits
Product ruby-saml
Weakness CWE-347
Published December 9, 2025
Last update December 9, 2025
View on NVD All CVEs

CVSS base score

9.3/10
Attack vector Network
Attack complexity Low
Privileges required None
User interaction None
Confidentiality —
Integrity —

CVSS vector

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N

What the vulnerability does

01Description

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.

Key dates

02Disclosure timeline

December 9, 2025 CVE published
December 9, 2025 Record updated