CVE-2026-31833
March 10, 2026
Umbraco is an ASP.NET CMS. From 16.2.0 to before 16.5.1 and 17.2.2, An authenticated backoffice user with access to Settings can inject malicious HTML into property type descriptions. Due to an overly permissive attributeNameCheck configuration (/.+/) in the UFM DOMPurify instance, event handler attributes such as onclick and onload, when used within Umbraco web components (umb-, uui-, ufm-*) were not filtered. This vulnerability is fixed in 16.5.1 and 17.2.2.
Affected Packages
umbraco.cms (NUGET):
Affected version(s) >=17.0.0 <17.2.2Fix Suggestion:
Update to version 17.2.2Umbraco.Cms (NUGET):
Affected version(s) >=16.2.0 <16.5.1Fix Suggestion:
Update to version 16.5.1umbraco.cms (NUGET):
Affected version(s) >=16.2.0 <16.5.1Fix Suggestion:
Update to version 16.5.1Umbraco.Cms (NUGET):
Affected version(s) >=17.0.0 <17.2.2Fix Suggestion:
Update to version 17.2.2Additional Notes
The description of this vulnerability differs from MITRE.
Related Resources (3)
Do you need more information?
Contact UsCVSS v4
Base Score:
8.6
Attack Vector
NETWORK
Attack Complexity
LOW
Attack Requirements
NONE
Privileges Required
HIGH
User Interaction
NONE
Vulnerable System Confidentiality
HIGH
Vulnerable System Integrity
HIGH
Vulnerable System Availability
LOW
Subsequent System Confidentiality
NONE
Subsequent System Integrity
NONE
Subsequent System Availability
NONE
CVSS v3
Base Score:
6.7
Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
HIGH
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
HIGH
Integrity
HIGH
Availability
LOW
Weakness Type (CWE)
Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
EPSS
Base Score:
0.06
