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High, CVSS 8.7amended

xmldom: End-tag Whitespace-Trim Regex ReDoS — quadratic backtracking in the 0.8.x end-tag parser

CVE-2026-83619GHSA-x4fp-j954-r2f4

What to do

Vendor fix available. Upgrade each affected package to the fixed version on its release line (@xmldom/xmldom 0.8.15), redeploy, then verify what is actually installed.

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

Sources

Severity and exploitation
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:N/VA:H/SC:N/SI:N/SA:N · score source
EPSS
  • CVE-2026-83619: 0.52% estimated exploitation activity in the next 30 days; percentile 44.48 (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 On the @xmldom/xmldom 0.8.x line, parsing an XML end tag whose name is followed by a long run of whitespace and then a non-whitespace character triggers quadratic-time regular-expression backtracking (ReDoS), so a single small crafted end tag stalls the Node.js event loop. It is reachable from DOMParser.parseFromString under default options, unauthenticated, before any validity check — an availability-only denial of service. The 0.9.x line is not affected. Details lib/sax.js (release-0.8.x, commit e5c1480) trims trailing whitespace from a captured end-tag name with an unanchored global regex: - lib/sax.js line 120: https://github.com/xmldom/xmldom/blob/e5c14802592685bb872c042c54c3f73758875c85/lib/sax.js#L120 Applied to a string shaped whitespace-run + one non-whitespace char (e.g. the content of an end tag </ … x), the engine must, for every starting position, extend [ws]+ to the end and then fail the $ anchor when the trailing non-whitespace char is present — classic O(n²)…

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

    Amended from ghsa record GHSA-x4fp-j954-r2f4

  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-x4fp-j954-r2f4

  4. Revision 1 · created ·

    Published from ghsa record GHSA-x4fp-j954-r2f4

Agent brief

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# Patch Next advisory brief: CVE-2026-83619

Advisory: xmldom: End-tag Whitespace-Trim Regex ReDoS — quadratic backtracking in the 0.8.x end-tag parser
IDs: CVE-2026-83619, GHSA-x4fp-j954-r2f4
Record: https://patchnext.com/advisories/cve-2026-83619 (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: Vendor fix available; fixed versions by package: @xmldom/xmldom 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; fixed in 0.8.15

## 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`.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on @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-x4fp-j954-r2f4 (GitHub-reviewed advisory GHSA-x4fp-j954-r2f4 lists affected ranges: npm @xmldom/xmldom >=0.7.0 <=0.8.14)
- Verified: https://osv.dev/vulnerability/GHSA-x4fp-j954-r2f4 (OSV record GHSA-x4fp-j954-r2f4 lists affected ranges: npm @xmldom/xmldom >=0.7.0 <0.8.15 (fixed))

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