GHSA-rhcg-3h8r-v6vp CVE-2026-31834
Umbraco Affected by Vertical Privilege Escalation via Missing Authorization Checks
- Severity
- 7.2 / 10
- High · CVSS 3.1
- Exploit chance (EPSS)
- 0.36%
- Chance of exploitation in the next 30 days. Higher than 29.22% of scored vulnerabilities.
- Known exploited
- No
- Not in CISA's catalog
- Weakness
- CWE-269 Improper Privilege Management
- Fix
16.5.1- Upgrade Umbraco.Cms to this version or later
Description
Description
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.
Impact
An authenticated backoffice user may be able to escalate their privileges to Administrator level.
Successful exploitation results in full administrative control of the affected Umbraco CMS instance, including unrestricted access to content, user management, and configuration settings.
The impact is significantly mitigated by the fact that this can only be exploited by a user that has already been given access to the "Users" section in the CMS. For most Umbraco setups, such users are already also "Administrators".
Patches
The issue is patched in 16.5.1 and 17.2.2.
Workarounds
There is no workaround other than upgrading for setups where they want to have users with permission for the "Users" section without also being content with those users also being part of the "Administrators" user group.
Affected versions
NuGet
| Package | Vulnerable | Fixed in |
|---|---|---|
| Umbraco.Cms | >= 15.3.1, < 16.5.1 |
16.5.1 |
| Umbraco.Cms | >= 17.0.0, < 17.2.2 |
17.2.2 |
How to fix
Move to the fixed version or later with your package manager, update the lockfile, and run your tests. If the package only arrives through another dependency, upgrade that dependency first. If none of its releases pulls a fixed version yet, force the version with your package manager's override.
Umbraco.Cms NuGet → 16.5.1
- dotnet
dotnet add package Umbraco.Cms --version 16.5.1
Severity breakdown
CVSS 3.1 7.2
CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H
- Attack vector
- Network
- Attack complexity
- Low
- Privileges required
- High
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- High
Weakness
CWE-269: Improper Privilege Management
The product does not properly assign, modify, track, or check privileges for an actor, creating an unintended sphere of control for that actor.
How to prevent it
- Architecture and Design, Operation: Very carefully manage the setting, management, and handling of privileges. Explicitly manage trust zones in the software.
- Architecture and Design: Follow the principle of least privilege when assigning access rights to entities in a software system.
- Architecture and Design: Consider following the principle of separation of privilege. Require multiple conditions to be met before permitting access to a system resource.
References
Advisories
Packages
Other links
Timeline
- Published
- Last updated by the source
- Latest EPSS score
Related advisories
| Advisory | Severity | Why it's related |
|---|---|---|
| GHSA-wr57-hqmp-fgvh Umbraco: Delivery API leaks protected (Public Access) content through Content Picker / Multi-Node Tree Picker expansion | High | Also affects Umbraco.Cms |
| GHSA-vr9v-27gg-qgx4 Umbraco.Cms: XSS/HTML Injection in Umbraco Backoffice confirmation dialog | Medium | Also affects Umbraco.Cms |
| GHSA-2qjj-h6wp-c7h7 Umbraco.Cms: Open Redirect Vulnerability in Surface Controllers | Medium | Also affects Umbraco.Cms |
| GHSA-vrqc-59mw-qqg7 Umbraco has Stored XSS in UFM Rendering Pipeline via Permissive DOMPurify Attribute Filtering | Medium | Also affects Umbraco.Cms |
| GHSA-fpvf-fvp5-996r Umbraco Backoffice API Allows Unauthorized Modification of Domain Data | Medium | Also affects Umbraco.Cms |
| GHSA-54mj-vcvj-q3v5 Umbraco CMS has an arbitrary file upload vulnerability | Critical | Also affects Umbraco.Cms |
| GHSA-hfv2-pf68-m33x Umbraco Vulnerable to Improper File Access and Credential Exposure in Dictionary Import Functionality | Medium | Also affects Umbraco.Cms |
| GHSA-pgvc-6h2p-q4f6 Umbraco CMS disclosure of configured password requirements | Medium | Also affects Umbraco.Cms |
MergeHarbor checks every repository's dependencies against this database, ranks what matters by exploitability and reachability, routes it to the owning team and opens the fix pull request.
Check your repos with MergeHarbor