How severe is CVE-2026-31833?

CVE-2026-31833 has a CVSS 3.x base score of 6.7, rated medium severity. It is exploitable over network with low attack complexity, requires high privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability low.

Is CVE-2026-31833 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (17th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-31833?

CVE-2026-31833 affects Umbraco Umbraco Cms. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-31833?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

Does CVE-2026-31833 have an EU (EUVD) identifier?

Yes. CVE-2026-31833 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-10936.

When was CVE-2026-31833 published?

CVE-2026-31833 was published on 2026-03-10 and last updated on 2026-06-17.

CVE-2026-31833

CVE-2026-31833 is a medium-severity vulnerability in Umbraco Umbraco Cms with a CVSS 3.x base score of 6.7. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-79.

Key facts

Severity: Medium (CVSS 3.x base score 6.7)
EPSS exploit prediction: 0% (17th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-10936
Weakness: CWE-79
Affected product: Umbraco Umbraco Cms
Published: 2026-03-10
Last modified: 2026-06-17

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.

Frequently asked questions

What is 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.
How severe is CVE-2026-31833?: CVE-2026-31833 has a CVSS 3.x base score of 6.7, rated medium severity. It is exploitable over network with low attack complexity, requires high privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability low.
Is CVE-2026-31833 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (17th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-31833?: CVE-2026-31833 affects Umbraco Umbraco Cms. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-31833?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
Does CVE-2026-31833 have an EU (EUVD) identifier?: Yes. CVE-2026-31833 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-10936.
When was CVE-2026-31833 published?: CVE-2026-31833 was published on 2026-03-10 and last updated on 2026-06-17.

References

https://github.com/umbraco/Umbraco-CMS/security/advisories/GHSA-vrqc-59mw-qqg7

Affected products (1)

cpe:2.3:a:umbraco:umbraco_cms:*:*:*:*:*:*:*:*

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