xmldom: Element name injection via createElement() bypasses requireWellFormed

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS 4.0

8.7 · 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 · score source

EPSS

• CVE-2026-83607: 0.61% estimated exploitation activity in the next 30 days; percentile 49.35 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary Document.createElement() in @xmldom/xmldom accepts arbitrary strings as the tagName parameter with zero validation. The serializer emits the tag name verbatim into XML/HTML output. Critically, the requireWellFormed: true serializer option — the recommended mitigation from CVE-2026-41672, CVE-2026-41674, and CVE-2026-34601 — did NOT catch this, making it a bypass of the existing security controls. An attacker who controls the element name string can inject arbitrary attributes (including event handlers) into the serialized output, leading to XSS when the output is consumed by a browser or downstream parser. Details Document.createElement() accepts any string as tagName and stores it directly on the element node without validation. When the document is later serialized via XMLSerializer.serializeToString(), the serializer emits the tagName verbatim into the output. The XML specification requires element names to conform to the Name production. The existing createAttributeNS()…

Published by the source

8 Sep 2026, 20:31 UTC

Last modified by the source

8 Sep 2026, 20:45 UTC

Source last checked

26 Oct 2026, 13:02 UTC

1. Revision 4 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-w2rr-34g9-rvrj

2. Revision 3 · amended · 25 Oct 2026

   Reviewed OSV alias/range/CVSS4 correction; package source scopes and original publication preserved. No customer finding resolved.

3. Revision 2 · amended · 24 Oct 2026

   Amended from osv record GHSA-w2rr-34g9-rvrj

4. Revision 1 · created · 23 Oct 2026

   Published from ghsa record GHSA-w2rr-34g9-rvrj

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# Patch Next advisory brief: CVE-2026-83607

Advisory: xmldom: Element name injection via createElement() bypasses requireWellFormed
IDs: CVE-2026-83607, GHSA-w2rr-34g9-rvrj
Record: https://patchnext.com/advisories/cve-2026-83607 (revision 4, source checked 26 Oct 2026, 13:02 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 8.7)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Partial vendor fix; fixed versions by package: @xmldom/xmldom 0.9.11, 0.8.14. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm @xmldom/xmldom: affected >= 0.9.0, <= 0.9.10; >= 0.7.0, <= 0.8.13; fixed in 0.9.11, 0.8.14
- npm xmldom: affected <= 0.6.0

## Suggested inspection (read-only)
- `npm ls @xmldom/xmldom --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.
- `npm ls xmldom --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.

## Supported action
No complete vendor fix is recorded. Follow the primary source's mitigation guidance and check this record again before closing anything.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on @xmldom/xmldom, xmldom.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-w2rr-34g9-rvrj (GitHub-reviewed advisory GHSA-w2rr-34g9-rvrj lists affected ranges: npm @xmldom/xmldom >=0.9.0 =0.7.0 =0 <=0.6.0)
- Verified: https://osv.dev/vulnerability/GHSA-w2rr-34g9-rvrj (OSV record GHSA-w2rr-34g9-rvrj lists affected ranges: npm @xmldom/xmldom >=0.9.0 =0.7.0 =0 <=0.6.0)

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