DOMPurify: Hook mutation of data.allowedTags / data.allowedAttributes permanently pollutes DEFAULT_ALLOWED_TAGS / DEFAULT_ALLOWED_ATTR

Exploitation

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

CVSS

6.1 · CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

EPSS

• CVE-2026-65902: 0.36% estimated exploitation activity in the next 30 days; percentile 29.29 (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.

Hook mutation of data.allowedTags / data.allowedAttributes permanently pollutes DEFAULTALLOWEDTAGS / DEFAULTALLOWEDATTR CWE: CWE-501 (Trust Boundary Violation — hook-scoped mutation leaks to global default sets) via CWE-693 (Protection Mechanism Failure — the default allow-list is silently widened for all subsequent sanitize calls) Summary The data.allowedTags and data.allowedAttributes fields passed to uponSanitizeElement and uponSanitizeAttribute hooks are direct references to the library's live ALLOWEDTAGS / ALLOWEDATTR sets. For sanitize calls that don't supply an explicit cfg.ALLOWEDTAGS / cfg.ALLOWEDATTR array, those live sets are themselves direct references to the module-level DEFAULTALLOWEDTAGS / DEFAULTALLOWEDATTR constants. A hook that mutates these fields — a natural-looking pattern for "allow X for this iteration" — permanently writes new entries into the default constants for the DOMPurify instance's lifetime. Every subsequent sanitize call that doesn't override the…

Published by the source

15 Jun 2026, 19:59 UTC

Last modified by the source

10 Sep 2026, 03:50 UTC

Source last checked

26 Oct 2026, 12:58 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-76mc-f452-cxcm

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-76mc-f452-cxcm

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# Patch Next advisory brief: CVE-2026-65902

Advisory: DOMPurify: Hook mutation of `data.allowedTags` / `data.allowedAttributes` permanently pollutes `DEFAULT_ALLOWED_TAGS` / `DEFAULT_ALLOWED_ATTR`
IDs: CVE-2026-65902, GHSA-76mc-f452-cxcm
Record: https://patchnext.com/advisories/cve-2026-65902 (revision 2, source checked 26 Oct 2026, 12:58 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 6.1)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: dompurify 3.4.7. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm dompurify: affected < 3.4.7; fixed in 3.4.7

## Suggested inspection (read-only)
- `npm ls dompurify --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 dompurify.
- 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-76mc-f452-cxcm (OSV record GHSA-76mc-f452-cxcm lists affected ranges: npm dompurify >=0 <3.4.7 (fixed))
- Verified: https://github.com/advisories/GHSA-76mc-f452-cxcm (GitHub-reviewed advisory GHSA-76mc-f452-cxcm lists affected ranges: npm dompurify >=0 <3.4.7)

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