CVE-2026-31834: Umbraco CMS

High severity, CVSS 7.2. EPSS: 0.5% chance of exploitation in the next 30 days.

Umbraco is an ASP.NET CMS. From 15.3.1 to before 16.5.1 and 17.2.2, A privilege escalation vulnerability has been identified in Umbraco CMS. Under certain conditions, authenticated backoffice users with permission to manage users, may be able to elevate their privileges due to insufficient authorization enforcement when modifying user group memberships. The affected functionality does not properly validate whether a user has sufficient privileges to assign highly privileged roles. This vulnerability is fixed in 16.5.1 and 17.2.2.

Affected products

• Umbraco Umbraco CMS: from 15.3.1, before 16.5.1 (fixed in 16.5.1); from 17.0.0, before 17.2.2 (fixed in 17.2.2)

Published 2026-03-10. Last modified 2026-06-17.