CVE-2026-65911 DOMPurify before 3.4.0 XSS via ADD_ATTR/ADD_TAGS State Leakage
State leakage in DOMPurify allows XSS when mixing function and array configurations for ADD_ATTR or ADD_TAGS across sanitize calls.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- Available
What is CVE-2026-65911?
CVE-2026-65911 is a medium-severity cross-site scripting vulnerability in cure53 DOMPurify, published on 23 Jul 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Official description
In DOMPurify through 3.3.3, function predicates supplied via ADD_ATTR or ADD_TAGS to DOMPurify.sanitize() persist in internal state (EXTRA_ELEMENT_HANDLING) across subsequent sanitize() calls on the same instance. If a later call on the same instance provides ADD_ATTR or ADD_TAGS as an array rather than a function, the previously set function handler is neither cleared nor overwritten, so it continues to approve attacker-controlled attributes or tags. This can allow dangerous event-handler attributes or forbidden tags (bypassing FORBID_TAGS) to survive sanitization, resulting in cross-site scripting. The vendor (Cure53) considers this an edge case outside DOMPurify's threat model; the referenced advisory lists 3.4.0 as the patched version.
Weakness: CWE-79
Which versions are affected by CVE-2026-65911?
It affects 1 product.
Products include Cure53 Dompurify.
How do I fix CVE-2026-65911?
Upgrade to a fixed version.
Escape output for the context it lands in and set a strict Content Security Policy. Upgrading the affected component is the real fix. More about Cross-site scripting.
Is CVE-2026-65911 being exploited?
There is no known exploitation of CVE-2026-65911 in the wild and no public exploit code.
Other vulnerabilities in cure53 DOMPurify
- CVE-2024-47875 DOMPurify nesting-based mXSS
- CVE-2024-48910 DOMPurify vulnerable to tampering by prototype polution
- CVE-2026-47423 DOMPurify XSS via `selectedcontent` re-clone
- CVE-2024-45801 Tampering by prototype polution in DOMPurify
- CVE-2026-49978 DOMPurify IN_PLACE Sanitization Bypass via Attached Shadow Root Inside <template>.content
Sources
Also known as DEBIAN-CVE-2026-65911, GHSA-9p3w-6h5p-cv75, UBUNTU-CVE-2026-65911.