The Nokogiri maintainers have evaluated this as High Severity 7.5 (CVSS3.0) for JRuby users. (This security advisory does not apply to CRuby users.)
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:
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.
github.com/rubysec/ruby-advisory-db/blob/master/gems/nokogiri/CVE-2021-41098.yml
github.com/sparklemotion/nokogiri
github.com/sparklemotion/nokogiri/commit/5bf729ff3cc84709ee3c3248c981584088bf9f6d
github.com/sparklemotion/nokogiri/security/advisories/GHSA-2rr5-8q37-2w7h
nvd.nist.gov/vuln/detail/CVE-2021-41098