Affected: Alpaquita:23: ruby-nokogiri, Alpaquita:25: ruby-nokogiri, Alpaquita:stream: ruby-nokogiri

Affected: Homebrew: mikutter

## 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`.

Nokogiri versions before 1.19.1 fail to check the return value from xmlC14NExecute in the canonicalize method, returning an empty string on failure instead of raising an exception. Attackers can exploit this to bypass signature validation in downstream SAML libraries by providing invalid canonicalized XML that is incorrectly accepted as valid.

Affected: RubyGems: nokogiri

## 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`.

Affected: Ubuntu:Pro:14.04:LTS: ruby-nokogiri, Ubuntu:16.04:LTS: ruby-nokogiri, Ubuntu:18.04:LTS: ruby-nokogiri, Ubuntu:Pro:20.04:LTS: ruby-nokogiri, Ubuntu:Pro:22.04:LTS: ruby-nokogiri, Ubuntu:24.04:LTS: ruby-nokogiri, Ubuntu:26.04:LTS: ruby-nokogiri

Nokogiri versions before 1.19.1 fail to check the return value from xmlC14NExecute in the canonicalize method, returning an empty string on failure instead of raising an exception. Attackers can exploit this to bypass signature validation in downstream SAML libraries by providing invalid canonicalized XML that is incorrectly accepted as valid.