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VulnerabilityPublished

CVE-2026-31834: Umbraco-CMS · Improper Privilege Management

Affects Umbraco-CMSSource CVE Database V5

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Not known to be exploited · CVSS 7.2 High : upgrade to 17.2.1 or 16.5.1 soon.

Data as of 30 Oct 2026, 11:52 UTC

CVSS 3.1 base score
7.2High
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.3% chance of exploitation in 30 days – higher than 29% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch
Available – fixed in 17.2.1, 16.5.1, 17.2.2
CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 10 Mar 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 30 Oct 2026.

What to do

Upgrade Umbraco-CMS to 17.2.1 or 16.5.1; umbraco-cms to 17.2.2 or 16.5.1.

Affected software

ProductAffectedFixed in
umbracoUmbraco-CMSAffected
  • >=17.0.0 <17.2.1
Fixed in
  • 17.2.1
umbracoUmbraco-CMSAffected
  • >=15.3.1 <16.5.1
Fixed in
  • 16.5.1
NuGetumbraco-cmspkg:nuget/umbraco-cmsOther threatsAffected
  • >=15.3.1 <16.5.1
  • >=17.0.0 <17.2.2
Fixed in
  • 16.5.1
  • 17.2.2

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

Organizations should immediately identify if they are running affected versions of Umbraco CMS (>=15.3.1 and <16.5.1, or >=17.0.0 and <17.2.2) and plan to upgrade to the patched versions 16.5.1 or 17.2.2 without delay. Until patching is possible, restrict user management permissions strictly to trusted administrators and audit all user group membership changes. Implement strong authentication and monitoring on backoffice accounts to detect unusual privilege escalations. Employ network segmentation and access controls to limit exposure of the CMS backend. Regularly review and enforce the principle of least privilege for all CMS users. Additionally, enable logging and alerting on privilege modification events to quickly identify potential exploitation attempts. Consider deploying Web Application Firewalls (WAFs) with custom rules to detect anomalous requests targeting user management endpoints. Finally, maintain an incident response plan to address potential compromises stemming from privilege escalation.

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.

References

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