Nokogiri versions before 1.16.5 bundle libxml2 2.12.6, which is affected by CVE-2024-34459 in libxml2's xmllint tool. Nokogiri 1.16.5 upgrades the bundled libxml2 to 2.12.7 to address this. Per the maintainers, there is no impact to Nokogiri users because Nokogiri does not provide or expose the xmllint tool where the issue occurs.

Nokogiri before 1.14.3 (CRuby implementation only, when using the packaged libxml2) bundles libxml2 v2.10.3, which is vulnerable to NULL pointer dereferences in XML Schema processing (xmlSchemaFixupComplexType, CVE-2023-28484, and xmlSchemaCheckCOSSTDerivedOK). An attacker who supplies a crafted/malformed XML schema can cause libxml2 to dereference a NULL pointer and potentially segfault, resulting in a denial of service. Nokogiri 1.14.3 upgrades the packaged libxml2 to v2.10.4 to resolve these issues.