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

Umbraco is an ASP.NET CMS. Due to unsafe handling and deletion of temporary files in versions 10.0.0 through 13.12.0, 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. This issue is fixed in version 13.12.1.

Source published

9 Dec 2025 20:09:27 UTC

Source modified

12 Dec 2025 20:33:09 UTC

Observed here

23 Oct 2026 15:48:27 UTC

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