CVE-2025-66568 ruby-saml Libxml2 Canonicalization errors can bypass Digest/Signature validation
Attackers can bypass SAML signature validation via libxml2 canonicalization errors, allowing unauthorized access to applications using ruby-saml.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2025-66568?
CVE-2025-66568 is a critical authentication bypass vulnerability in SAML-Toolkits ruby-saml, published on 9 Dec 2025. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
The ruby-saml library implements the client side of an SAML authorization. Versions up to and including 1.12.4, are vulnerable to authentication bypass through the libxml2 canonicalization process used by Nokogiri for document transformation, which allows an attacker to execute a Signature Wrapping attack. When libxml2’s canonicalization is invoked on an invalid XML input, it may return an empty string rather than a canonicalized node. ruby-saml then proceeds to compute the DigestValue over this empty string, treating it as if canonicalization succeeded. This issue is fixed in version 1.18.0.
Weakness: CWE-347
Which versions are affected by CVE-2025-66568?
2 open source packages ship an affected version, including ruby-saml. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
ruby-saml RubyGems | All versions | 1.18.0 |
ruby-saml RubyGems | All versions | 1.18.0 |
Products include Onelogin Ruby-Saml.
How do I fix CVE-2025-66568?
Upgrade ruby-saml to 1.18.0 or later.
Upgrade, and rotate credentials and sessions that may have been exposed. More about Authentication bypass.
Is CVE-2025-66568 being exploited?
There is no known exploitation of CVE-2025-66568 in the wild and no public exploit code.
Other vulnerabilities in SAML-Toolkits ruby-saml
- CVE-2015-20108 ruby-saml vulnerable to XPath injection
- CVE-2025-66567 ruby-saml has a SAML authentication bypass due to namespace handling (parser differential)
- CVE-2017-11428 Multiple SAML libraries may allow authentication bypass via incorrect XML canonicalization and DOM traversal
- CVE-2016-5697 Ruby-saml allows attackers to perform XML signature wrapping attacks
Sources
Also known as GHSA-x4h9-gwv3-r4m4, UBUNTU-CVE-2025-66568.