CVE-2026-83608: xmldom DocType name injection bypasses requireWellFormed

CVE-2026-83608 · Severity: high · CVSS 4 · Published 2026-09-01

The xmldom XML serializer emits the DocumentType name field without validation, allowing attackers to inject arbitrary markup (XML elements, comments, or scripts) by breaking out of the DOCTYPE declaration. Applications using the recommended `requireWellFormed: true` mitigation for other xmldom injection flaws remain vulnerable through this unguarded name field, risking markup injection and XSS attacks if the serialized output is processed by a browser or XML parser.

Technologies: @xmldom/xmldom (npm), xmldom (npm). Vendors: npm.

Quick answers

Is CVE-2026-83608 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-83608 being exploited in the wild.
How severe is CVE-2026-83608?
High severity, with a CVSS score of 4, published 1 September 2026.
Which products and versions are affected?
@xmldom/xmldom (npm) SEMVER:introduced=0.7.0,fixed=0.8.15; xmldom (npm) SEMVER:introduced=0,last_affected=0.6.0.
Is there a fix for CVE-2026-83608?
Yes. @xmldom/xmldom (npm): upgrade to 0.8.15 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-83608 attacked?
It is attacked with local access, in a software library.
Am I affected by CVE-2026-83608?
Check whether you run @xmldom/xmldom (npm) or xmldom (npm) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

How to fix

  • @xmldom/xmldom (npm): upgrade to 0.8.15 or later
    npm install @xmldom/xmldom@0.8.15

Technical details

This is an XML markup injection vulnerability in the serialization logic of the xmldom DOM implementation. The `XMLSerializer.serializeToString()` method emits a DocumentType node's `name` field directly into the `<!DOCTYPE ...>` declaration without any well-formedness validation, even when `requireWellFormed: true` is specified. An attacker can craft a malicious name (e.g., `html><script>alert(1)</script`) that breaks out of the DOCTYPE declaration via a `>` character, injecting sibling elements or comments. The vulnerability stems from incomplete hardening in a prior fix (GHSA-f6ww-3ggp-fr8h): that fix validated `publicId`, `systemId`, and `internalSubset` fields but omitted the `name` field. On 0.8.x and the legacy unscoped `xmldom` package, the name is also unvalidated at DocumentType creation time, allowing direct injection via `createDocumentType()`. On 0.9.x, the name is validated at creation but left writable, so an attacker can bypass creation-time checks via direct property assignment. The fix adds validation of the name field under `requireWellFormed: true`, throwing `InvalidStateError` if it violates the XML Name production, but protection remains opt-in and not automatic.

Affected products

  • xmldom @xmldom/xmldom 0.7.0–0.8.14, 0.9.0–0.9.11
  • xmldom xmldom ≤ 0.6.0 (unscoped, no patch available)

Identifiers

  • CVE-2026-83608
  • GHSA-27p8-2357-5qqv

Timeline

  • 2026-08-21: disclosed: Vulnerability published in GitHub Advisory Database
  • 2026-09-08: advisory: Advisory updated; fix released for @xmldom/xmldom 0.8.15 and 0.9.12

References

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