CVE-2026-41238

DOMPurify: Prototype Pollution to XSS Bypass via CUSTOM_ELEMENT_HANDLING Fallback

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.

Affected

cure53 · DOMPurify

CVSS v3.1 GITHUB

6.9 MEDIUMCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:H/I:L/A:N

EPSS

0.35% chance of exploitation in the next 30 days, 27th percentile

Published

2026-04-23

Proof-of-concept exploits (2)

• advisories/GHSA-v9jr-rg53-9pgp
• snowcapped-morula414/bingo3★ · 2026-10-13

References

• CVE Record
• NVD entry

Related

• CVE-2026-10520
• CVE-2026-23631