Vulnerability · Published Sep 1, 2026 · Assigned by GitHub_M

CVE-2026-83618xmldom: requireWellFormed DocType publicId/systemId validation is bypassable via an embedded line terminator

High 8.7

In plain English

A high-severity security flaw in xmldom from xmldom. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.6% (higher than 47% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 4.0)8.7High

Exploit odds (30 days)0.6%top 52.6% of all CVEs

Exploited in the wildNo reportsCISA SSVC: poc

Attack toolingNoneno public tooling known

Official description

xmldom is a pure JavaScript W3C standard-based (XML DOM Level 2 Core) DOMParser and XMLSerializer module. From 0.9.10 until 0.9.12, the requireWellFormed: true serializer validates DocumentType.publicId and DocumentType.systemId with PubidLiteral_match and SystemLiteral_match expressions produced by reg() in lib/grammar.js, which inherit the multiline flag. A complete valid literal on the first line can therefore satisfy the matcher while U+000A, U+000D, U+2028, or U+2029 and breakout markup remain in the emitted <!DOCTYPE ...> declaration. This bypasses the strict-serialization mitigation for the earlier DocumentType injection advisory; creation and direct property assignment remain unvalidated by design. This issue is fixed in @xmldom/xmldom version 0.9.12.

Affected packages & fixed versions

Ecosystem	Package	Fixed in	Advisory
Debian:12	node-xmldom	no fix listed	DEBIAN-CVE-2026-83618
Debian:13	node-xmldom	no fix listed	DEBIAN-CVE-2026-83618
Debian:14	node-xmldom	0.9.12-1	DEBIAN-CVE-2026-83618
Ubuntu:22.04:LTS	node-xmldom	no fix listed	UBUNTU-CVE-2026-83618
Ubuntu:24.04:LTS	node-xmldom	no fix listed	UBUNTU-CVE-2026-83618
Ubuntu:26.04:LTS	node-xmldom	no fix listed	UBUNTU-CVE-2026-83618
Ubuntu:26.10	node-xmldom	no fix listed	UBUNTU-CVE-2026-83618
npm	@xmldom/xmldom	0.9.12	GHSA-vr34-hp96-76pp

Affected products (as reported)

Vendor	Product	Versions
xmldom	xmldom	>= 0.9.10, < 0.9.12
@xmldom	xmldom	>= 0.9.10, < 0.9.12

Weakness: CWE-91, CWE-625 · Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N

References

https://github.com/xmldom/xmldom/security/advisories/GHSA-vr34-hp96-76pp x_refsource_CONFIRM
https://github.com/xmldom/xmldom/pull/1071 x_refsource_MISC
https://github.com/xmldom/xmldom/commit/7b2ec67e1750daadd0bb06c92e875e726544a362 x_refsource_MISC
https://github.com/xmldom/xmldom/releases/tag/0.9.12 x_refsource_MISC