Umbraco Vulnerable to Improper File Access and Credential Exposure in Dictionary Import Functionality

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

4.9 · CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:N/A:N

EPSS

• CVE-2025-66625: 0.36% estimated exploitation activity in the next 30 days; percentile 29.54 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Impact Due to unsafe handling and deletion of temporary files during the dictionary upload process, an attacker with access to the backoffice can trigger predictable requests to temporary file paths. The application’s error responses (HTTP 500 when a file exists, 404 when it does not) allow the attacker to enumerate the existence of arbitrary files on the server’s filesystem. This vulnerability does not allow reading or writing file contents. In certain configurations, incomplete clean-up of temporary upload files may additionally expose the NTLM hash of the Windows account running the Umbraco application. The direct impact of this vulnerability is therefore limited to confidentiality, which is reflected in its CVSS base score of 4.9 While the CVSS Base Score captures only the immediate effect, the practical risk varies significantly based on hosting environment and identity configuration. Umbraco Cloud sites run under low-privilege, isolated Azure App Service worker identities,…

Published by the source

9 Dec 2025, 17:12 UTC

Last modified by the source

9 Dec 2025, 21:37 UTC

Source last checked

26 Oct 2026, 17:04 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-hfv2-pf68-m33x

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# Patch Next advisory brief: CVE-2025-66625

Advisory: Umbraco Vulnerable to Improper File Access and Credential Exposure in Dictionary Import Functionality
IDs: CVE-2025-66625, GHSA-hfv2-pf68-m33x
Record: https://patchnext.com/advisories/cve-2025-66625 (revision 1, source checked 26 Oct 2026, 17:04 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 4.9)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: umbraco.cms 13.12.1. A vendor fix does not mean a deployment is fixed.

## Affected components
- NuGet umbraco.cms: affected >= 10.0.0, <= 13.12.0; fixed in 13.12.1

## Suggested inspection (read-only)
- NuGet umbraco.cms: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on umbraco.cms.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-hfv2-pf68-m33x (GitHub-reviewed advisory GHSA-hfv2-pf68-m33x lists affected ranges: NuGet umbraco.cms >=10.0.0 <=13.12.0)

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