CVE-2026-41240 | THREATINT

Description

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.

PUBLISHED Reserved 2026-04-18 | Published 2026-04-23 | Updated 2026-04-23 | Assigner GitHub_M

MEDIUM: 6.0CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N

Problem types

CWE-183: Permissive List of Allowed Inputs

CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

Product status

< 3.4.0

affected

References

github.com/...Purify/security/advisories/GHSA-h7mw-gpvr-xq4m exploit

github.com/...Purify/security/advisories/GHSA-h7mw-gpvr-xq4m

github.com/...ommit/c361baa18dbdcb3344a41110f4c48ad85bf48f80

github.com/cure53/DOMPurify/releases/tag/3.4.0

cve.org (CVE-2026-41240)

nvd.nist.gov (CVE-2026-41240)

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