Vulnerability Intelligence Report
DOMPurify: Prototype Pollution to XSS Bypass via CUSTOM_ELEMENT_HANDLING Fallback
CVE-2026-41238
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.
No Active Exploit Signals
CVSS Base Score
6.9
MEDIUM
Exploitability:1.7
Impact Score:4.8
EPSS Probability:0.21%
Executive Threat Verdict
Evaluating...
Evaluating Threat Landscape...
Assessing known weaponization, exploitation telemetry, and federal advisories.
Attack Surface
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Authentication
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Weaponization
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SSVC Action
—
Weaknesses (CWE)
CWE-79 ↗CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
CWE-1321 ↗CWE-1321: Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution')
Affected Products & Versions
| Vendor | Product | Affected Versions |
|---|---|---|
| cure53 | DOMPurify | >= 3.0.1, < 3.4.0 (affected) |
References & Technical Advisories
No reference links found.
Threat Intelligence Signals
EPSS Score
0.205%
GitHub Advisory
Identity & Timeline
| Status | PUBLISHED |
| Assigning Authority | GitHub, Inc. · Vendor · USA |
| Reserved | 2026-04-18T03:47:03 |
| Published | 2026-04-23T14:43:17 |
| Last Updated | 2026-04-23T16:22:34 |
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