Improper Restriction of XML External Entity Reference (XXE) in Nokogiri on JRuby
### Severity
The Nokogiri maintainers have evaluated this as **High Severity** 7.5 (CVSS3.0)
https://www.first.org/cvss/calculator/3.0#CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N/E:H/RL:O/RC:C/MAV:N/MAC:L for JRuby users. (This security advisory does not apply to CRuby users.)
### Impact
In Nokogiri v1.12.4 and earlier, **on JRuby only**, the SAX parser resolves external entities by default.
Users of Nokogiri on JRuby who parse untrusted documents using any of these classes are affected:
- Nokogiri::XML::SAX::Parser
- Nokogiri::HTML4::SAX::Parser or its alias Nokogiri::HTML::SAX::Parser
- Nokogiri::XML::SAX::PushParser
- Nokogiri::HTML4::SAX::PushParser or its alias Nokogiri::HTML::SAX::PushParser
### Mitigation
JRuby users should upgrade to Nokogiri v1.12.5 or later. There are no workarounds available for v1.12.4 or earlier.
CRuby users are not affected.