HTML Injection Vulnerability in Umbraco CMS by Umbraco
CVE-2026-31833

6.7MEDIUM

Key Information:

Vendor

Umbraco

Status
Umbraco-cms
Vendor
CVE Published:
10 March 2026

What is CVE-2026-31833?

Umbraco is an ASP.NET-based Content Management System (CMS) that, between versions 16.2.0 and before 16.5.1, as well as version 17.2.2, is susceptible to an HTML injection vulnerability. This flaw allows authenticated backoffice users with access to Settings to inject malicious HTML into property type descriptions due to a permissive configuration in the UFM DOMPurify instance. Notably, event handler attributes like onclick and onload are not adequately filtered when used in Umbraco web components (umb-, uui-, ufm-*), potentially leading to further exploitation. The vulnerability has been resolved in versions 16.5.1 and 17.2.2.

Affected Version(s)

Umbraco-CMS >= 16.2.0, < 16.5.1 < 16.2.0, 16.5.1

Umbraco-CMS >= 17.0.0, < 17.2.1 < 17.0.0, 17.2.1

References

https://github.com/umbraco/Umbraco-CMS/security/advisorie...
x_refsource_CONFIRM

CVSS V3.1

Score:
6.7
Severity:
MEDIUM
Confidentiality:
High
Integrity:
High
Availability:
High
Attack Vector:
Network
Attack Complexity:
Low
Privileges Required:
High
User Interaction:
None
Scope:
Unchanged

Timeline

  • Vulnerability published

  • Vulnerability Reserved

.