CVE-2026-126063

Nokogiri: Mutation XSS through `noscript` content in Nokogiri's HTML5 serializer

Published Nov 10, 2026 CVSS 4.0 · 2.3 Low EPSS < 1% KEV · Not listed
Description
Nokogiri is an open source XML and HTML library for the Ruby programming language. From 1.12.0 until 1.19.5, the C extension on CRuby and TruffleRuby has a Nokogiri::HTML5 serializer that does not escape text inside noscript elements or angle brackets inside attribute values. When an application sanitizes untrusted HTML with the default parsing options, allows noscript, and sends serialized output to a scripting-enabled browser, the browser can parse markup that Nokogiri did not produce, enabling mutation cross-site scripting. Using parse_noscript_content_as_text: true is the recommended workaround, not the vulnerable default. JRuby is not affected because it does not implement Nokogiri::HTML5. This issue is fixed in version 1.19.5.

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

Source ID Title
Github GHSA Github GHSA GHSA-4p39-36wj-23h4 Nokogiri: Mutation XSS through `noscript` content in Nokogiri's HTML5 serializer
History
Type Values Removed Values Added
First Time appeared Sparklemotion
Sparklemotion nokogiri
Vendors & Products Sparklemotion
Sparklemotion nokogiri
Type Values Removed Values Added
Description Nokogiri is an open source XML and HTML library for the Ruby programming language. From 1.12.0 until 1.19.5, the C extension on CRuby and TruffleRuby has a Nokogiri::HTML5 serializer that does not escape text inside noscript elements or angle brackets inside attribute values. When an application sanitizes untrusted HTML with the default parsing options, allows noscript, and sends serialized output to a scripting-enabled browser, the browser can parse markup that Nokogiri did not produce, enabling mutation cross-site scripting. Using parse_noscript_content_as_text: true is the recommended workaround, not the vulnerable default. JRuby is not affected because it does not implement Nokogiri::HTML5. This issue is fixed in version 1.19.5.
Title Nokogiri: Mutation XSS through `noscript` content in Nokogiri's HTML5 serializer
Weaknesses CWE-116
CWE-79
References
Metrics cvssV4_0

{'score': 2.3, 'vector': 'CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
GitHub_M
Published
Updated
Nov 10, 2026, 8:14 PM
Reserved
Nov 10, 2026, 5:07 PM
Status
Awaiting Analysis
Published
Nov 10, 2026, 9:19 PM
Modified
Nov 12, 2026, 10:18 PM