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MEDIUM · 6.7

CVE-2026-31833

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...

Vulnerability Description

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.

CVSS Score

6.7

MEDIUM

CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:L
Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
HIGH
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
HIGH
Integrity
HIGH
Availability
LOW

Affected Products

VendorProductVersions
UmbracoUmbraco Cms>= 16.2.0, < 16.5.1

Related Weaknesses (CWE)

CWE-79

References

FAQ

What is CVE-2026-31833?

CVE-2026-31833 is a vulnerability with a CVSS score of 6.7 (MEDIUM). 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...

How severe is CVE-2026-31833?

CVE-2026-31833 has been rated MEDIUM with a CVSS base score of 6.7/10. Review the CVSS metrics above for detailed severity breakdown.

Is there a patch for CVE-2026-31833?

Check the references section above for vendor advisories and patch information. Affected products include: Umbraco Umbraco Cms.