CVE-2026-31833 json
Umbraco has Stored XSS in UFM Rendering Pipeline via Permissive DOMPurify Attribute Filtering
published 7mo ago modified 4mo ago also EUVD-2026-10936 , GHSA-vrqc-59mw-qqg7
- cvss
- 6.7
- version 3.1, CNA
- cisa kev
- Not listed
- not in CISA's catalog
- epss
- 0.3%
- EPSS 0.3% chance of exploitation in 30 days, percentile 23%
- public exploits
- 0
- none known
Summary
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.
Patch / fix
- nuget Umbraco.Cms 16.5.1, 17.2.2
- umbraco umbraco_cms 16.5.1, 17.2.1
Is CVE-2026-31833 in your dependencies? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.
Check with FencerCISA SSVC
- Exploitation
- none
- Automatable
- no
- Technical impact
- total
- Assessed
- 7mo ago
Exploit prediction
0.30% chance of exploitation in the next 30 days, higher than 23% of all scored CVEs (FIRST EPSS, 2026-11-09).
CVSS scores
| assigned by | version | score | vector |
|---|---|---|---|
| CNA | 3.1 | 6.7 | CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:L |
| GitHub | 3.1 | 6.7 | CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:L |
Affected packages
| ecosystem | package | affected | fixed in |
|---|---|---|---|
| nuget | Umbraco.Cms | >=16.2.0, <16.5.1 >=17.0.0, <17.2.2 |
16.5.1 17.2.2 |
Affected products
- umbraco Umbraco-CMS
Classification
- Weakness
-
- CWE-79 Improper Neutralization of Input During Web Page Generation
References
-
github.com
/umbraco/Umbraco-CMS/security/advisories/GHSA-vrqc-59mw-qqg7
web, vendor-advisory
-
nvd.nist.gov
/vuln/detail/CVE-2026-31833
advisory
-
github.com
/umbraco/Umbraco-CMS
package
Sources
- CVE List CVE-2026-31833
- GitHub Advisory GHSA-vrqc-59mw-qqg7
- NVD CVE-2026-31833
Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.
CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.