CVE-2026-41238 DOMPurify: Prototype Pollution to XSS Bypass via CUSTOM_ELEMENT_HANDLING Fallback
Prototype pollution allows bypassing DOMPurify sanitization, enabling XSS attacks via injected custom elements and attributes.
- 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-2026-41238?
CVE-2026-41238 is a medium-severity cross-site scripting vulnerability in cure53 DOMPurify, published on 23 Apr 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. Versions 3.0.1 through 3.3.3 are vulnerable to a prototype pollution-based XSS bypass. When an application uses `DOMPurify.sanitize()` with the default configuration (no `CUSTOM_ELEMENT_HANDLING` option), a prior prototype pollution gadget can inject permissive `tagNameCheck` and `attributeNameCheck` regex values into `Object.prototype`, causing DOMPurify to allow arbitrary custom elements with arbitrary attributes — including event handlers — through sanitization. Version 3.4.0 fixes the issue.
Which versions are affected by CVE-2026-41238?
2 open source packages ship an affected version, including dompurify.
| Package | Affected | Fixed in |
|---|---|---|
dompurify npm | From 3.0.1 | 3.4.0 |
dompurify npm | From 3.0.1 | 3.4.0 |
How do I fix CVE-2026-41238?
Upgrade dompurify to 3.4.0 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-2026-41238 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-41238 exists.
Sources
Also known as CLEANSTART-2026-AM93725, CLEANSTART-2026-NT67628, DEBIAN-CVE-2026-41238, ECHO-951f-211f-5fc7, GHSA-v9jr-rg53-9pgp, MINI-3gqp-x9f3-2wrx and 12 more.