Vulnerability Details 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 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.
Exploit prediction scoring system (EPSS) score
EPSS Score 0.001
EPSS Ranking 17.2%
CVSS Severity
CVSS v3 Score 6.7
Products affected by CVE-2026-31833
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cpe:2.3:a:umbraco:umbraco_cms:*
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cpe:2.3:a:umbraco:umbraco_cms:16.2.0