DOMPurify: Cross-realm IN_PLACE sanitization leaves executable markup intact via realm-bound instanceof checks

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-2026-49458: 0.40% estimated exploitation activity in the next 30 days; percentile 34.73 (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.

Cross-realm INPLACE sanitization leaves executable markup intact via realm-bound instanceof checks CWE: CWE-79 (XSS — Improper Neutralization of Input During Web Page Generation) via CWE-693 (Protection Mechanism Failure — realm-bound instanceof checks fail-open on foreign-realm DOM nodes) and CWE-501 (Trust Boundary Violation — foreign-realm nodes accepted for sanitization but later checks are bound to the parent realm) Summary DOMPurify.sanitize(node, { INPLACE: true }) accepts a DOM node from any same-origin realm (e.g. a node owned by an application-created iframe document), but several follow-on security checks compare the node against constructors from the parent realm. Because constructors are per-realm, instanceof HTMLFormElement, instanceof NamedNodeMap, instanceof DocumentFragment, and instanceof Element all return false for nodes belonging to the iframe's realm. The library therefore proceeds as if the foreign-realm form is not clobberable, the foreign-realm <template's…

Published by the source

15 Jun 2026, 19:56 UTC

Last modified by the source

10 Sep 2026, 03:50 UTC

Source last checked

26 Oct 2026, 12:55 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-hpcv-96wg-7vj8

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-hpcv-96wg-7vj8

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# Patch Next advisory brief: CVE-2026-49458

Advisory: DOMPurify: Cross-realm IN_PLACE sanitization leaves executable markup intact via realm-bound `instanceof` checks
IDs: CVE-2026-49458, GHSA-hpcv-96wg-7vj8
Record: https://patchnext.com/advisories/cve-2026-49458 (revision 2, source checked 26 Oct 2026, 12:55 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 3.4.6. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm dompurify: affected <= 3.4.5; fixed in 3.4.6

## 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-hpcv-96wg-7vj8 (OSV record GHSA-hpcv-96wg-7vj8 lists affected ranges: npm dompurify >=0 <3.4.6 (fixed))
- Verified: https://github.com/advisories/GHSA-hpcv-96wg-7vj8 (GitHub-reviewed advisory GHSA-hpcv-96wg-7vj8 lists affected ranges: npm dompurify >=0 <=3.4.5)

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