Umbraco CMS up to 16.5.0/17.2.1 Group Membership privileges management

CVSS Meta Temp Score
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CTI Interest Score
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5.8$0-$5k0.00

Summaryinfo

A vulnerability was found in Umbraco CMS up to 16.5.0/17.2.1 and classified as critical. This issue affects some unknown processing of the component Group Membership Handler. Executing a manipulation can lead to privileges management. This vulnerability is registered as CVE-2026-31834. It is possible to launch the attack remotely. No exploit is available. It is suggested to upgrade the affected component.

Detailsinfo

A vulnerability classified as critical was found in Umbraco CMS up to 16.5.0/17.2.1. This vulnerability affects an unknown code of the component Group Membership Handler. The manipulation with an unknown input leads to a privileges management vulnerability. The CWE definition for the vulnerability is 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. As an impact it is known to affect confidentiality, integrity, and availability. CVE summarizes:

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.

The advisory is shared for download at github.com. This vulnerability was named CVE-2026-31834 since 03/09/2026. The exploitation appears to be easy. The attack can be initiated remotely. The exploitation requires an enhanced level of successful authentication. There are neither technical details nor an exploit publicly available. The MITRE ATT&CK project declares the attack technique as T1068.

Upgrading to version 16.5.1 or 17.2.2 eliminates this vulnerability.

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Productinfo

Type

Vendor

Name

Version

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 5.9
VulDB Meta Temp Score: 5.8

VulDB Base Score: 4.7
VulDB Temp Score: 4.5
VulDB Vector: 🔒
VulDB Reliability: 🔍

CNA Base Score: 7.2
CNA Vector (GitHub_M): 🔒

CVSSv2info

AVACAuCIA
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VectorComplexityAuthenticationConfidentialityIntegrityAvailability
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VulDB Base Score: 🔒
VulDB Temp Score: 🔒
VulDB Reliability: 🔍

Exploitinginfo

Class: Privileges management
CWE: CWE-269 / CWE-266
CAPEC: 🔒
ATT&CK: 🔒

Physical: No
Local: No
Remote: Yes

Availability: 🔒
Status: Not defined

EPSS Score: 🔒
EPSS Percentile: 🔒

Price Prediction: 🔍
Current Price Estimation: 🔒

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Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: Upgrade
Status: 🔍

0-Day Time: 🔒

Upgrade: CMS 16.5.1/17.2.2

Timelineinfo

03/09/2026 CVE reserved
03/10/2026 +1 days VulDB entry created
03/11/2026 +0 days Advisory disclosed
03/16/2026 +5 days VulDB entry last update

Sourcesinfo

Advisory: GHSA-rhcg-3h8r-v6vp
Status: Confirmed

CVE: CVE-2026-31834 (🔒)
GCVE (CVE): GCVE-0-2026-31834
GCVE (VulDB): GCVE-100-350200

Entryinfo

Created: 03/11/2026 00:06
Updated: 03/16/2026 07:27
Changes: 03/11/2026 00:06 (66), 03/16/2026 07:27 (1)
Complete: 🔍
Cache ID: 216:C78:103

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