Auth bypass in Umbraco Umbraco-Cms
CVE-2026-31834
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.
Vulnerability class: Privilege Escalation
EPSS: 0.003 (17.7th percentile) — read the EPSS interpretation.
CVSS v3 metric
CVSS v3 base score 7.2 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H.
Affected products
- Umbraco Umbraco-cms — versions >= 15.3.1, < 16.5.1, >= 17.0.0, < 17.2.1
- Umbraco Umbraco_cms
Weakness classification (CWE)
References
- security-advisories@github.com (x_refsource_CONFIRM, Vendor Advisory)
Frequently asked questions
- What is CVE-2026-31834?
- CVE-2026-31834 is a high-severity vulnerability in Umbraco Umbraco-Cms, classified under Improper Privilege Management. CVSS score: 7.2/10. Published 2026-03-10.
- How severe is CVE-2026-31834?
- High severity. CVSS v3 base score is 7.2 out of 10.