Umbraco Affected by Vertical Privilege Escalation via Missing Authorization Checks

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

7.2 · CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H

EPSS

• CVE-2026-31834: 0.36% estimated exploitation activity in the next 30 days; percentile 29.26 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

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…

Published by the source

11 Mar 2026, 14:54 UTC

Last modified by the source

11 Mar 2026, 14:54 UTC

Source last checked

26 Oct 2026, 17:04 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-rhcg-3h8r-v6vp

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# Patch Next advisory brief: CVE-2026-31834

Advisory: Umbraco Affected by Vertical Privilege Escalation via Missing Authorization Checks
IDs: CVE-2026-31834, GHSA-rhcg-3h8r-v6vp
Record: https://patchnext.com/advisories/cve-2026-31834 (revision 1, source checked 26 Oct 2026, 17:04 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 7.2)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: umbraco.cms 17.2.2, 16.5.1. A vendor fix does not mean a deployment is fixed.

## Affected components
- NuGet umbraco.cms: affected >= 15.3.1, < 16.5.1; >= 17.0.0, < 17.2.2; fixed in 16.5.1, 17.2.2

## Suggested inspection (read-only)
- NuGet umbraco.cms: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on umbraco.cms.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-rhcg-3h8r-v6vp (GitHub-reviewed advisory GHSA-rhcg-3h8r-v6vp lists affected ranges: NuGet umbraco.cms >=15.3.1 =17.0.0 <17.2.2)

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