CVE-2026-31834
Privilege Escalation in Umbraco CMS via User Group Misauthorization
Publication date: 2026-03-10
Last updated on: 2026-03-18
Assigner: GitHub, Inc.
Description
Description
CVSS Scores
EPSS Scores
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Meta Information
Affected Vendors & Products
| Vendor | Product | Version / Range |
|---|---|---|
| umbraco | umbraco_cms | From 15.3.1 (inc) to 16.5.1 (exc) |
| umbraco | umbraco_cms | From 17.0.0 (inc) to 17.2.2 (exc) |
Helpful Resources
Exploitability
| CWE ID | Description |
|---|---|
| CWE-284 | The product does not restrict or incorrectly restricts access to a resource from an unauthorized actor. |
| CWE-862 | The product does not perform an authorization check when an actor attempts to access a resource or perform an action. |
| CWE-269 | The product does not properly assign, modify, track, or check privileges for an actor, creating an unintended sphere of control for that actor. |
Attack-Flow Graph
AI Powered Q&A
How can this vulnerability be detected on my network or system? Can you suggest some commands?
I don't know
Can you explain this vulnerability to me?
This vulnerability is a privilege escalation issue in Umbraco CMS versions from 15.3.1 to before 16.5.1 and 17.2.2. Authenticated backoffice users who have permission to manage users may be able to increase their privileges improperly. This happens because the system does not sufficiently enforce authorization checks when these users modify user group memberships, allowing them to assign highly privileged roles without proper validation.
How can this vulnerability impact me? :
The impact of this vulnerability is that an authenticated user with some administrative permissions could escalate their privileges to gain higher-level access than intended. This could lead to unauthorized access to sensitive data, modification of critical settings, or further compromise of the system's integrity, confidentiality, and availability.
How does this vulnerability affect compliance with common standards and regulations (like GDPR, HIPAA)?:
I don't know
What immediate steps should I take to mitigate this vulnerability?
To mitigate this vulnerability, you should upgrade Umbraco CMS to version 16.5.1 or 17.2.2, where the privilege escalation issue has been fixed.
Additionally, review and restrict permissions for authenticated backoffice users who have the ability to manage users, ensuring they do not have unnecessary privileges to assign highly privileged roles.