XSS in Cure53 Dompurify
CVE-2026-41240
DOMPurify is a DOM-only cross-site scripting sanitizer for HTML, MathML, and SVG. Versions prior to 3.4.0 have an inconsistency between FORBID_TAGS and FORBID_ATTR handling when function-based ADD_TAGS is used. Commit c361baa added an early exit for FORBID_ATTR at line 1214. The same fix was not applied to FORBID_TAGS. At line 1118-1123, when EXTRA_ELEMENT_HANDLING.tagCheck returns true, the short-circuit evaluation skips the FORBID_TAGS check entirely. This allows forbidden elements to survive sanitization with their attributes intact. Version 3.4.0 patches the issue.
Vulnerability class: XSS (Cross-Site Scripting)
Published · last modified .
CVSS v3 metric
CVSS v3 base score 6.1 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N.
EPSS exploit prediction
EPSS: 0.004 (33.1th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 33rd percentile — 33.1% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.003 · newest: 0.004 · change: +0.001
Affected products
- Cure53 Dompurify — versions < 3.4.0
Weakness classification (CWE)
References
- github.com/cure53/DOMPurify/security/advisories/GHSA-h7mw-gpvr-xq4m (Exploit, Patch, Mitigation, Vendor Advisory)
- github.com/cure53/DOMPurify/commit/c361baa18dbdcb3344a41110f4c48ad85bf48f80 (Patch)
- github.com/cure53/DOMPurify/releases/tag/3.4.0 (Product, Release Notes)
Frequently asked questions
- What is CVE-2026-41240?
- CVE-2026-41240 is a medium-severity vulnerability in Cure53 Dompurify, classified under Cross-site Scripting. CVSS score: 6.1/10. Published 2026-04-23.
- How severe is CVE-2026-41240?
- Medium severity. CVSS v3 base score is 6.1 out of 10.