Improper access control in DOMPurify - CVE-2026-65903
Published: April 16, 2026 / Updated: September 14, 2026
Vulnerability identifier: #VU126319
CSH Severity: Medium
CVSS v4: 5.3 [CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-65903
CWE-ID: CWE-284
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote user to bypass tag filtering restrictions.
The vulnerability exists due to improper access control in the ADD_TAGS tag handling logic when processing sanitized HTML with both ADD_TAGS as a function and FORBID_TAGS enabled. A remote user can supply crafted markup using forbidden tags to bypass tag filtering restrictions.
Only applications that use ADD_TAGS in function form together with FORBID_TAGS are affected.
Affected software
DOMPurify
Fedora
nextcloud
Fedora
nextcloud
How to mitigate CVE-2026-65903
Install security update from vendor's website.
DOMPurify - update to 3.4.0
nextcloud - addressed in versions 34.0.3-1.el10_2, 34.0.3-1.el10_3, 34.0.3-1.fc44
nextcloud - addressed in versions 34.0.3-1.el10_2, 34.0.3-1.el10_3, 34.0.3-1.fc44