High severity · published Mar 10, 2026
CVE-2026-31834
Umbraco Affected by Vertical Privilege Escalation via Missing Authorization Checks
7.2
CVSS
0.4%
EPSS
No
On KEV
Description
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.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H
Attack vector
Network
Complexity
Low
Privileges
High
User interaction
None
Confidentiality
High
Integrity
High
Availability
High
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.4% · higher than 29% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
UM
Umbraco-CMS · umbraco
>= 15.3.1, < 16.5.1; >= 17.0.0, < 17.2.1 · source: vendor
UC
Umbraco Cms · Umbraco
15.3.1 before 16.5.1; 17.0.0 before 17.2.2 · source: NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-31834
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-31834
Vendor Advisory
https://github.com/umbraco/Umbraco-CMS/security/advisories/GHSA-rhcg-3h8r-v6vp
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