CVE-2026-41238CWE-1321CWE-79

DOMPurify: Prototype Pollution to XSS Bypass via CUSTOM_ELEMENT_HANDLING Fallback

Medium · published April 23, 2026

CVSS v3.1
6.9
EPSS
0%
Percentile
26.9
In the wild
Unconfirmed
What it is

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.

The record
Technical detail
CVSS v3.1
6.9 · MEDIUM
Vector
CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:H/I:L/A:N
CVSS v4.0
Not supplied
EPSS
0.00346 · 26.9th percentile
Weaknesses
CWE-1321 · Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution'); CWE-79 · Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
Published
2026-04-23T14:43Z
EPSS history
Timeline
  • 23 APR 14:43Z
    DOMPurify: Prototype Pollution to XSS Bypass via CUSTOM_ELEMENT_HANDLING Fallback
    cvelistv5