DOMPurify has a SAFE_FOR_TEMPLATES bypass in RETURN_DOM mode

Exploitation

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

CVSS

6.8 · CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N

EPSS

• CVE-2026-41239: 0.25% estimated exploitation activity in the next 30 days; percentile 16.21 (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.

Summary | Field | Value | |:------|:------| | Severity | Medium | | Affected | DOMPurify main at 883ac15, introduced in v1.0.10 (7fc196db) | SAFEFORTEMPLATES strips {{...}} expressions from untrusted HTML. This works in string mode but not with RETURNDOM or RETURNDOMFRAGMENT, allowing XSS via template-evaluating frameworks like Vue 2. Technical Details DOMPurify strips template expressions in two passes: 1. Per-node — each text node is checked during the tree walk (purify.ts:1179-1191): 2. Final string scrub — after serialization, the full HTML string is scrubbed again (purify.ts:1679-1683). This is the safety net that catches expressions that only form after the DOM settles. The RETURNDOM path returns before pass #2 ever runs (purify.ts:1637-1661): The payload {<foo</foo{constructor.constructor('alert(1)')()}<foo</foo} exploits this: 1. Parser creates: TEXT("{") → <foo → TEXT("{payload}") → <foo → TEXT("}") — no single node contains {{, so pass #1 misses it 2. <foo is not allowed,…

Published by the source

22 Apr 2026, 17:32 UTC

Last modified by the source

10 Sep 2026, 03:50 UTC

Source last checked

26 Oct 2026, 12:51 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-crv5-9vww-q3g8

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-crv5-9vww-q3g8

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# Patch Next advisory brief: CVE-2026-41239

Advisory: DOMPurify has a SAFE_FOR_TEMPLATES bypass in RETURN_DOM mode
IDs: CVE-2026-41239, GHSA-crv5-9vww-q3g8
Record: https://patchnext.com/advisories/cve-2026-41239 (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: Medium (CVSS 6.8)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: dompurify 3.4.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm dompurify: affected >= 1.0.10, < 3.4.0; fixed in 3.4.0

## 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-crv5-9vww-q3g8 (OSV record GHSA-crv5-9vww-q3g8 lists affected ranges: npm dompurify >=1.0.10 <3.4.0 (fixed))
- Verified: https://github.com/advisories/GHSA-crv5-9vww-q3g8 (GitHub-reviewed advisory GHSA-crv5-9vww-q3g8 lists affected ranges: npm dompurify >=1.0.10 <3.4.0)

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