Nokogiri does not check the return value from xmlC14NExecute
Date: 2026-02
Affected: rubygems/nokogiri
Attack vector: other
Category: vulnerability-disclosure
Severity: Medium
CWE: CWE-252
CVSS: 5.3 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N)

## Summary Nokogiri's CRuby extension fails to check the return value from `xmlC14NExecute` in the method `Nokogiri::XML::Document#canonicalize` and `Nokogiri::XML::Node#canonicalize`. When canonicalization fails, an empty string is returned instead of raising an exception. This incorrect return value may allow downstream libraries to accept invalid or incomplete canonicalized XML, which has been demonstrated to enable signature validation bypass in SAML libraries. JRuby is not affected, as the Java implementation correctly raises `RuntimeError` on canonicalization failure. ## Mitigation Upgrade to Nokogiri `>= 1.19.1`. ## Severity The maintainers have assessed this as **Medium** severity. Nokogiri itself is a parsing library without a clear security boundary related to canonicalization, so the direct impact is that a method returns incorrect data on invalid input. However, this behavior was exploited in practice to bypass SAML signature validation in downstream libraries (see References). ## Credit This vulnerability was responsibly reported by HackerOne researcher `d4d`.


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