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

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-126063
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-11-10 21:19:23 UTC
Updated2026-11-10 21:19:23 UTC
DescriptionNokogiri 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.

Risk And Classification

Primary CVSS: v4.0 2.3 LOW from [email protected]

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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Problem Types: CWE-79 | CWE-116 | CWE-79 CWE-79: Improper Neutralization of Input During Web Page Generation | CWE-116 CWE-116: Improper Encoding or Escaping of Output

VersionSourceTypeScoreSeverityVector
4.0[email protected]Secondary2.3LOWCVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N/E:X/C...
4.0CNADECLARED2.3LOWCVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N

CVSS v4.0 Breakdown

Attack Vector
Network
Attack Complexity
Low
Attack Requirements
Present
Privileges Required
None
User Interaction
Passive
Confidentiality
None
Integrity
None
Availability
None
Sub Conf.
Low
Sub Integrity
Low
Sub Availability
None

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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Sparklemotion Nokogiri affected >= 1.12.0, < 1.19.5 Not specified

References

ReferenceSourceLinkTags
github.com/sparklemotion/nokogiri/commit/3e84df6ff7ab4d78f446e3a415430bd... [email protected] github.com
github.com/sparklemotion/nokogiri/security/advisories/GHSA-4p39-36wj-23h4 [email protected] github.com
github.com/sparklemotion/nokogiri/releases/tag/v1.19.5 [email protected] github.com
github.com/sparklemotion/nokogiri/commit/c6c0bffbdcd194694995acafeeed273... [email protected] github.com
github.com/sparklemotion/nokogiri/pull/3752 [email protected] github.com
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