What’s Vulnerable › Vulnerabilities

CVE-2026-41240: DOMPurify: FORBID_TAGS bypassed by function-based ADD_TAGS predicate (asymmetry with FORBID_ATTR fix)

• Severity: medium (CVSS 6.1 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.3% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2026-04-23 · updated 2026-10-26
• Weakness: CWE-79

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.

Affected products

• cure53 DOMPurify: before 3.4.0 — fixed in 3.4.0

How to fix

Upgrade to a fixed version: cure53 DOMPurify 3.4.0. Check the vendor advisory for mitigations.

References

• https://github.com/cure53/DOMPurify/commit/c361baa18dbdcb3344a41110f4c48ad85bf48f80
• https://github.com/cure53/DOMPurify/releases/tag/3.4.0
• https://github.com/cure53/DOMPurify/security/advisories/GHSA-h7mw-gpvr-xq4m
• https://github.com/cure53/DOMPurify/security/advisories/GHSA-h7mw-gpvr-xq4m

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