CVE-2026-49458 DOMPurify: Cross-realm IN_PLACE sanitization leaves executable markup intact via realm-bound `instanceof` checks
DOMPurify fails to sanitize cross-realm DOM nodes in IN_PLACE mode, allowing attackers to inject executable markup and achieve cross-site scripting.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- Available
What is CVE-2026-49458?
CVE-2026-49458 is a medium-severity cross-site scripting vulnerability in cure53 DOMPurify, published on 14 Jul 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Official description
DOMPurify is a DOM-only cross-site scripting sanitizer for HTML, MathML, and SVG. Prior to 3.4.6, DOMPurify.sanitize(node, { IN_PLACE: true }) accepted same-origin foreign-realm DOM nodes while follow-on checks used parent-realm constructors, causing instanceof checks for forms, named node maps, document fragments, and elements to fail and skip clobber, template-content, and shadow-DOM sanitization branches so executable markup could survive. This issue is fixed in version 3.4.6.
Which versions are affected by CVE-2026-49458?
2 open source packages ship an affected version, including dompurify. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
dompurify npm | All versions | 3.4.6 |
dompurify npm | All versions | 3.4.6 |
Products include Cure53 Dompurify.
How do I fix CVE-2026-49458?
Upgrade dompurify to 3.4.6 or later.
Escape output for the context it lands in and set a strict Content Security Policy. Upgrading the affected component is the real fix. More about Cross-site scripting.
Is CVE-2026-49458 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-49458 exists.
Other vulnerabilities in cure53 DOMPurify
- CVE-2024-47875 DOMPurify nesting-based mXSS
- CVE-2024-48910 DOMPurify vulnerable to tampering by prototype polution
- CVE-2026-47423 DOMPurify XSS via `selectedcontent` re-clone
- CVE-2024-45801 Tampering by prototype polution in DOMPurify
- CVE-2026-49978 DOMPurify IN_PLACE Sanitization Bypass via Attached Shadow Root Inside <template>.content
Sources
Also known as CLSA-2026-1785554485, DEBIAN-CVE-2026-49458, ECHO-620b-e534-5a35, GHSA-hpcv-96wg-7vj8, MINI-235q-85gv-mr4w, MINI-2864-2v5x-73q4 and 17 more.