ADVISORIES
GEM
SEVERITY
CVSS v3.x: 5.3 (Medium)
UNAFFECTED VERSIONS
- < 1.5.1
PATCHED VERSIONS
- >= 1.19.1
DESCRIPTION
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.