CVE-2021-41098: Improper Restriction of XML External Entity Reference (XXE) in Nokogiri on JRuby

Severity: high (CVSS 7.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 1.5% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2021-09-27 · updated 2026-06-17
Weakness: CWE-611

Description

Nokogiri is a Rubygem providing HTML, XML, SAX, and Reader parsers with XPath and CSS selector support. 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::Parse, Nokogiri::HTML4::SAX::Parser or its alias Nokogiri::HTML::SAX::Parser, Nokogiri::XML::SAX::PushParser, and Nokogiri::HTML4::SAX::PushParser or its alias Nokogiri::HTML::SAX::PushParser. JRuby users should upgrade to Nokogiri v1.12.5 or later to receive a patch for this issue. There are no workarounds available for v1.12.4 or earlier. CRuby users are not affected.

Affected products

sparklemotion nokogiri: before 1.12.5 — fixed in 1.12.5
Rubygems Nokogiri: before 1.12.5; 1.0.0, 1.0.1, 1.0.2, 1.0.3, 1.0.4, 1.0.5 (+132) — fixed in 1.12.5

How to fix

Upgrade to a fixed version: sparklemotion nokogiri 1.12.5; Rubygems Nokogiri 1.12.5. Check the vendor advisory for mitigations.

References

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