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Medium, CVSS 6.9amended

xmldom: Parser silently accepts a not-well-formed end tag whose name is followed by a line break and trailing content

CVE-2026-83611GHSA-6h8r-xr42-gp59

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
    >= 0.7.0, <= 0.8.14>= 0.9.0, <= 0.9.11
    Fixed in
    0.9.12, 0.8.15

  • 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 4.0
6.9 · CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N · score source
EPSS
  • CVE-2026-83611: 0.62% estimated exploitation activity in the next 30 days; percentile 49.73 (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's parser silently accepts a not-well-formed end tag whose valid name is followed by trailing content — e.g. </a⏎junk. The element is closed, the trailing content is discarded, and no error is reported, even though the XML end-tag production allows only optional whitespace after the name and both Chromium and Firefox reject such input as application/xml. An application that relies on xmldom to reject not-well-formed input therefore receives a false "valid" result for a document the specification and browsers consider malformed. Details Across every affected version, an end tag whose valid Name is followed by trailing content before is silently accepted: the element is closed, the residue is dropped, and no error is reported. How much leaks differs by line (see Affected Versions), but the observable weakness is the same. On the current (0.9.x) line, the parser validates the end-tag name against the XML ETag production with an anchored regular expression (^ QName S? $).…

Dates and revisions
Published by the source
Last modified by the source
Source last checked
  1. Revision 4 · amended ·

    Amended from ghsa record GHSA-6h8r-xr42-gp59

  2. Revision 3 · amended ·

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

  3. Revision 2 · amended ·

    Amended from osv record GHSA-6h8r-xr42-gp59

  4. Revision 1 · created ·

    Published from ghsa record GHSA-6h8r-xr42-gp59

Agent brief

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# Patch Next advisory brief: CVE-2026-83611

Advisory: xmldom: Parser silently accepts a not-well-formed end tag whose name is followed by a line break and trailing content
IDs: CVE-2026-83611, GHSA-6h8r-xr42-gp59
Record: https://patchnext.com/advisories/cve-2026-83611 (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: Medium (CVSS 6.9)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Partial vendor fix; fixed versions by package: @xmldom/xmldom 0.9.12, 0.8.15. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm @xmldom/xmldom: affected >= 0.7.0, <= 0.8.14; >= 0.9.0, <= 0.9.11; fixed in 0.9.12, 0.8.15
- 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-6h8r-xr42-gp59 (GitHub-reviewed advisory GHSA-6h8r-xr42-gp59 lists affected ranges: npm @xmldom/xmldom >=0.7.0 =0.9.0 =0 <=0.6.0)
- Verified: https://osv.dev/vulnerability/GHSA-6h8r-xr42-gp59 (OSV record GHSA-6h8r-xr42-gp59 lists affected ranges: npm @xmldom/xmldom >=0.7.0 =0.9.0 =0 <=0.6.0)

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