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Umbraco Cms CVE-2026-31833

MEDIUM
Cross-site Scripting (XSS) (CWE-79)
2026-03-10 security-advisories@github.com GHSA-vrqc-59mw-qqg7
XSS Umbraco Cms
6.7
CVSS 3.1 · GitHub Advisory
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Severity by source

GitHub Advisory PRIMARY
6.7 MEDIUM
AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:L

Primary rating from GitHub Advisory · only source for this CVE.

CVSS VectorGitHub Advisory

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

Lifecycle Timeline

3
Patch released
Mar 31, 2026 - 21:13 nvd
Patch available
Analysis Generated
Mar 12, 2026 - 21:55 vuln.today
CVE Published
Mar 10, 2026 - 22:16 nvd
MEDIUM 6.7

DescriptionGitHub Advisory

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.

AnalysisAI

Umbraco is an ASP.NET CMS. From 16.2.0 to versions up to 16.5.1 is affected by cross-site scripting (xss) (CVSS 6.7).

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Vulnerability AssessmentAI

Risk Assessment CVSS 6.7 (MEDIUM). … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in.
Exploit Scenario An attacker (requires authentication) could exploit this vulnerability to compromise the affected system.
Remediation Fixed in version 16.5.1. … Detailed patch versions, workarounds, and compensating controls in full report.
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Within 30 days: Identify affected systems and apply vendor patches as part of regular patch cycle. …

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CVE-2026-31833 vulnerability details – vuln.today
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