{"id":"CVE-2026-41238","aliases":["GHSA-v9jr-rg53-9pgp"],"url":"https://o3.security/vulnerability/CVE-2026-41238","summary":"DOMPurify: Prototype Pollution to XSS Bypass via CUSTOM_ELEMENT_HANDLING Fallback","details":"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.","published":"2026-04-23T14:43:17.730Z","modified":"2026-08-12T03:51:35.136067976Z","cvss":{"score":6.9,"severity":"MEDIUM","vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:H/I:L/A:N"},"epss":{"score":0.00225,"percentile":0.13351,"asOf":"2026-08-14"},"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"npm","name":"dompurify","fixedVersion":"3.4.0"}],"fix":null,"references":[{"type":"WEB","url":"https://github.com/cure53/DOMPurify/releases/tag/3.4.0"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/41xxx/CVE-2026-41238.json"},{"type":"ADVISORY","url":"https://github.com/cure53/DOMPurify/security/advisories/GHSA-v9jr-rg53-9pgp"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-41238"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-12T03:51:35.136067976Z"}}