CVE-2026-31833 MEDIUM

CVE-2026-31833: Umbraco has Stored XSS in UFM Rendering Pipeline via Permissive DOMPurify Attribute Filtering

Vendor Umbraco
Product Umbraco-CMS
Weakness CWE-79 · XSS
Published March 10, 2026
Last update March 11, 2026
View on NVD All CVEs

CVSS base score

6.7/10
Attack vector Network
Attack complexity Low
Privileges required High
User interaction None
Confidentiality High
Integrity High

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:L

What the vulnerability does

01Description

Umbraco is an ASP.NET CMS. From 16.2.0 to before 16.5.1 and 17.2.2, An authenticated backoffice user with access to Settings can inject malicious HTML into property type descriptions. Due to an overly permissive attributeNameCheck configuration (/.+/) in the UFM DOMPurify instance, event handler attributes such as onclick and onload, when used within Umbraco web components (umb-*, uui-*, ufm-*) were not filtered. This vulnerability is fixed in 16.5.1 and 17.2.2.

Key dates

02Disclosure timeline

March 10, 2026 CVE published
March 11, 2026 Record updated