Vulnerability in Umbraco ASP.NET CMS Affects Temporary File Handling

CVE-2025-66625

What is CVE-2025-66625?

Umbraco, a widely used ASP.NET Content Management System (CMS), has a vulnerability arising from improper handling of temporary files during the dictionary upload process. Attackers with access to the backoffice can exploit this flaw to issue predictable requests to temporary file paths. The application’s response behavior (HTTP 500 for existing files and 404 for non-existing files) enables attackers to enumerate the presence of arbitrary files within the server’s filesystem. Although the vulnerability does not allow direct access to file contents, certain configurations may inadvertently reveal the NTLM hash associated with the Windows account running Umbraco. This issue impacts versions 10.0.0 to 13.12.0 and has been addressed in version 13.12.1.

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