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CVE-2026-31834— Umbraco Affected by Vertical Privilege Escalation via Missing Authorization Checks

Quick assessment

Affected
umbraco Umbraco-CMS
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Umbraco是丹麦Umbraco公司的一套C#编写的开源的内容管理系统（CMS）。 Umbraco 15.3.1版本至16.5.1之前版本和17.2.2之前版本存在安全漏洞，该漏洞源于修改用户组成员身份时授权执行不足，可能导致权限提升。

CVSS 7.2 · High EPSS 0.46% · P38

Possible ATT&CK Techniques 1 AI

T1078 · Valid Accounts
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I. Basic Information for CVE-2026-31834

Vulnerability Information
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Vulnerability Title
Umbraco Affected by Vertical Privilege Escalation via Missing Authorization Checks
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
特权管理不恰当
Source: CVE Program / CVE List V5
Vulnerability Title
Umbraco 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Umbraco是丹麦Umbraco公司的一套C#编写的开源的内容管理系统（CMS）。 Umbraco 15.3.1版本至16.5.1之前版本和17.2.2之前版本存在安全漏洞，该漏洞源于修改用户组成员身份时授权执行不足，可能导致权限提升。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
umbraco Umbraco-CMS >= 15.3.1, < 16.5.1 -

II. Public POCs for CVE-2026-31834

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III. Intelligence Information for CVE-2026-31834

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Vendor Advisories for CVE-2026-31834 (1)

Same Patch Batch · umbraco · 2026-03-10 · 3 CVEs total

CVE-2026-31833 6.7 MEDIUM Umbraco has Stored XSS in UFM Rendering Pipeline via Permissive DOMPurify Attribute Filter
CVE-2026-31832 5.4 MEDIUM Umbraco Backoffice API Allows Unauthorized Modification of Domain Data

IV. Related Vulnerabilities

Same product: Umbraco-CMS
Same vendor: umbraco
Same weakness: CWE-269

V. Comments for CVE-2026-31834

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