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High, CVSS 7.5amended

xmldom: XML injection via unsafe CDATA serialization allows attacker-controlled markup insertion

CVE-2026-34601GHSA-wh4c-j3r5-mjhp

What to do

Partial vendor fix. Follow the primary source's mitigation guidance and check back for a fix.

This page has no inventory attached, so it cannot say whether you are affected. A vendor fix is not proof that your deployment is fixed.

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Affected packages

  • npm @xmldom/xmldom

    Affected
    < 0.8.12>= 0.9.0, < 0.9.9
    Fixed in
    0.9.9, 0.8.12

  • npm xmldom

    Affected
    <= 0.6.0
    Fixed in
    no fixed version recorded

Sources

Severity and exploitation
Exploitation
No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.
CVSS
7.5 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
EPSS
  • CVE-2026-34601: 0.49% estimated exploitation activity in the next 30 days; percentile 42.20 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.
Source description

As published by the source; long descriptions are shortened.

Summary @xmldom/xmldom allows attacker-controlled strings containing the CDATA terminator ]] to be inserted into a CDATASection node. During serialization, XMLSerializer emitted the CDATA content verbatim without rejecting or safely splitting the terminator. As a result, data intended to remain text-only became active XML markup in the serialized output, enabling XML structure injection and downstream business-logic manipulation. The sequence ]] is not allowed inside CDATA content and must be rejected or safely handled during serialization. (MDN Web Docs) Attack surface Document.createCDATASection(data) is the most direct entry point, but it is not the only one. The WHATWG DOM spec intentionally does not validate ]] in mutation methods — only createCDATASection carries that guard. The following paths therefore also allow ]] to enter a CDATASection node and reach the serializer: - CharacterData.appendData() - CharacterData.replaceData() - CharacterData.insertData() - Direct assignment…

Dates and revisions
Published by the source
Last modified by the source
Source last checked
  1. Revision 2 · amended ·

    Amended from ghsa record GHSA-wh4c-j3r5-mjhp

  2. Revision 1 · created ·

    Published from osv record GHSA-wh4c-j3r5-mjhp

Agent brief

Preview the exact text before you copy it. Commands are read-only suggestions; review them before running anything.

# Patch Next advisory brief: CVE-2026-34601

Advisory: xmldom: XML injection via unsafe CDATA serialization allows attacker-controlled markup insertion
IDs: CVE-2026-34601, GHSA-wh4c-j3r5-mjhp
Record: https://patchnext.com/advisories/cve-2026-34601 (revision 2, source checked 26 Oct 2026, 12:51 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 7.5)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Partial vendor fix; fixed versions by package: @xmldom/xmldom 0.9.9, 0.8.12. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm @xmldom/xmldom: affected < 0.8.12; >= 0.9.0, < 0.9.9; fixed in 0.9.9, 0.8.12
- 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://osv.dev/vulnerability/GHSA-wh4c-j3r5-mjhp (OSV record GHSA-wh4c-j3r5-mjhp lists affected ranges: npm xmldom >=0 =0 =0.9.0 <0.9.9 (fixed))
- Verified: https://github.com/advisories/GHSA-wh4c-j3r5-mjhp (GitHub-reviewed advisory GHSA-wh4c-j3r5-mjhp lists affected ranges: npm xmldom >=0 =0 =0.9.0 <0.9.9)

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