CVE-2025-66568: Ruby saml Ruby-saml Allows A Libxml2 Canonicalization Vulnerability

CRITICAL
Advisory Identifier: GHSA-x4h9-gwv3-r4m4
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CWE-347
Published
Advisory Summary

CVE-2025-66568 is a CRITICAL ruby-saml allows a libxml2 canonicalization vulnerability (CWE-347: Improper Verification of Cryptographic Signature) affecting Ruby saml libraries in the RubyGems ecosystem. The issue involves ruby-saml allows a libxml2 canonicalization error to bypass digest/signature validation. Remediation is available by upgrading affected packages to version 1.18.0.

CVE-2025-66568 at a Glance

CVE Identifier CVE-2025-66568
GHSA Identifier GHSA-x4h9-gwv3-r4m4
Severity CRITICAL
CVSS v3.1 Base Score N/A
CWE Classification CWE-347: Improper Verification of Cryptographic Signature
Affected Product Ruby saml
Package Ecosystem RubyGems
Published Date
Last Updated

How to Fix CVE-2025-66568

To remediate this vulnerability, upgrade all affected Ruby saml dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

ruby-saml fixed: 1.18.0 
Upgrade ruby-saml to 1.18.0
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

inspect dependencies for ruby-saml

How to Check if You Are Affected

To determine whether your application is affected by CVE-2025-66568, inspect your project dependencies for Ruby saml:

inspect dependencies for ruby-saml

Analyze the terminal output to locate any version of Ruby saml in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 1.18.0), your application is affected.

Note: Verify declared build manifests and deployed runtime container environments.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-347: Improper Verification of Cryptographic Signature, where the product does not verify, or incorrectly verifies, the cryptographic signature for data. In Ruby saml, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

### Summary Ruby-saml up to and including 1.12.4, there is an authentication bypass vulnerability because of an issue at libxml2 canonicalization process used by Nokogiri for document transformation. That allows an attacker to be able to execute a Signature Wrapping attack. The vulnerability does not affect the version 1.18.0. ### Details 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. ### Impact 1. Digest bypass: By crafting input that causes canonicalization to yield an empty string, the attacker can manipulate validation to pass incorrectly. 2. Signature replay on empty canonical form: If an empty string has been signed once (e.g., in a prior interaction or via a misconfigured flow), that signature can potentially be replayed to bypass authentication.

CVE-2025-66568 Affected Ruby saml Versions

1 component(s)
Fixed Versions:
1.18.0
Product / Package Ecosystem Affected Versions Fixed Version
ruby-saml
gem/ruby-saml
RubyGems
< 1.18.0
1.18.0

References

GitHub Advisory / Wiki ADVISORY
https://github.com/SAML-Toolkits/ruby-saml/security/advisories/GHSA-x4h9-gwv3-r4m4
NVD — CVE-2025-66568 NVD
https://nvd.nist.gov/vuln/detail/CVE-2025-66568
Security Fix Commit FIX COMMIT
https://github.com/SAML-Toolkits/ruby-saml/commit/acac9e9cc0b9a507882c614f25d41f8b47be349a
Ruby saml Source Repository REPOSITORY
https://github.com/SAML-Toolkits/ruby-saml
Ruby saml Source Repository REPOSITORY
https://github.com/rubysec/ruby-advisory-db/blob/master/gems/ruby-saml/CVE-2025-66568.yml

Frequently Asked Questions

What is CVE-2025-66568?
CVE-2025-66568 is a security vulnerability in Ruby saml involving Ruby-saml allows a Libxml2 Canonicalization error to bypass Digest/Signature validation under CWE-347: Improper Verification of Cryptographic Signature.
Which Ruby saml versions are affected?
Affected versions include releases prior to 1.18.0 across affected packages: ruby-saml.
What version fixes CVE-2025-66568?
Upgrading to 1.18.0 (or the latest patched release for your respective branch) resolves the vulnerability.
Is ruby-saml affected?
Yes, ruby-saml is affected in releases prior to 1.18.0. Upgrade your dependency to 1.18.0 or later.
What CWE is associated with CVE-2025-66568?
CVE-2025-66568 is classified under CWE-347: Improper Verification of Cryptographic Signature (The product does not verify, or incorrectly verifies, the cryptographic signature for data.).
How can I check RubyGems dependencies for CVE-2025-66568?
Run the dependency tree command: 'inspect dependencies for ruby-saml'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-x4h9-gwv3-r4m4",
  "modified" : "2025-12-12T21:52:40Z",
  "published" : "2025-12-08T22:03:19Z",
  "aliases" : [ "CVE-2025-66568" ],
  "summary" : "Ruby-saml allows a Libxml2 Canonicalization error to bypass Digest/Signature validation",
  "details" : "### Summary\nRuby-saml up to and including 1.12.4, there is an authentication bypass vulnerability because of an issue at libxml2 canonicalization process used by Nokogiri for document transformation. That allows an attacker to be able to execute a Signature Wrapping attack. The vulnerability does not affect the version 1.18.0.\n\n### Details\nWhen 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.\n\n### Impact\n1. Digest bypass: By crafting input that causes canonicalization to yield an empty string, the attacker can manipulate validation to pass incorrectly.\n\n2. Signature replay on empty canonical form: If an empty string has been signed once (e.g., in a prior interaction or via a misconfigured flow), that signature can potentially be replayed to bypass authentication.",
  "severity" : [ {
    "type" : "CVSS_V4",
    "score" : "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"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "RubyGems",
      "name" : "ruby-saml"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "1.18.0"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/SAML-Toolkits/ruby-saml/security/advisories/GHSA-x4h9-gwv3-r4m4"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2025-66568"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/SAML-Toolkits/ruby-saml/commit/acac9e9cc0b9a507882c614f25d41f8b47be349a"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/SAML-Toolkits/ruby-saml"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/rubysec/ruby-advisory-db/blob/master/gems/ruby-saml/CVE-2025-66568.yml"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-347" ],
    "severity" : "CRITICAL",
    "github_reviewed" : true,
    "github_reviewed_at" : "2025-12-08T22:03:19Z",
    "nvd_published_at" : "2025-12-09T16:18:21Z"
  }
}