VulnerabilityAnalyzed

CVE-2026-31833

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.

MEDIUM 6.7EPSS 0.26%

Does this matter?

Lower severity and a low EPSS score (0.26%). Track it; it rarely justifies an emergency change on its own.

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 3.1: 6.7 MEDIUMCVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:L
EPSS: 0.26% probability · 18th percentile
CISA KEV: Not listed
Weakness: CWE-79
Affected: umbraco/umbraco cms
Source: security-advisories@github.com

References

https://github.com/umbraco/Umbraco-CMS/security/advisories/GHSA-vrqc-59mw-qqg7Vendor Advisory

Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.