Administrator escalation via unchecked group membership assignment
Published Mar 10, 2026 · Updated Mar 10, 2026
Privilege escalation in Umbraco CMS 15.3.1 through 16.5.0 and 17.0.0 through 17.2.1 allows remote authenticated users to become administrators. User-group membership modification fails to verify that the acting backoffice account is authorized to assign the Administrator group. Exploitation requires existing backoffice access to the Users section and grants full control of CMS content, users, and configuration.
Summary
What happened
Privilege escalation in Umbraco CMS 15.3.1 through 16.5.0 and 17.0.0 through 17.2.1 allows remote authenticated users to become administrators. User-group membership modification fails to verify that the acting backoffice account is authorized to assign the Administrator group. Exploitation requires existing backoffice access to the Users section and grants full control of CMS content, users, and configuration.
The record
- CVE
- CVE-2026-31834
- Published
- Mar 10, 2026
- Updated
- Mar 10, 2026
- Vendor
- Umbraco
- Product
- Umbraco CMS
- Classifications
- CWE-862, CWE-284, CWE-269, T1098
- Attack vector
- network
- Privileges
- authenticated
Timeline
How it unfolded
- Mar 10, 2026CVE publishedPublication date reported by the CVE source.
- Mar 10, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=>= 15.3.1, < 16.5.1
- Affected versionversion=>= 17.0.0, < 17.2.1
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Weakness, pattern, technique
Public exploit references
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Technologies
Your stack
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Your stack
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