CVE-2020-5188

Vulnerability

Overview

CVE-2020-5188 describes an insecure permissions vulnerability in DNN (formerly DotNetNuke) that affects versions through 9.4.4. The issue allows an authenticated user to bypass file extension checks, potentially enabling the upload of executable or other dangerous file types that should otherwise be restricted. The vulnerability stems from inadequate permission validation during file upload operations.

Exploitation

Prerequisites

Exploitation requires an authenticated user account on a DNN site running version 9.4.4 or earlier. The attacker must have permissions to upload files through the platform's file management features. The vulnerability was publicly disclosed through a Packet Storm advisory that detailed the file extension check bypass in DNN CMS 9.5.0 (though the CVE covers through 9.4.4) [2]. Authentication is a prerequisite as the upload functionality is only available to logged-in users.

Impact

If successfully exploited, an authenticated attacker could upload arbitrary files with dangerous extensions (such as ASPX, PHP, or other executable types) to the web server. This could lead to remote code execution on the server, depending on server configuration and file execution permissions. The insecure permissions flaw effectively negates the platform's intended file type restrictions.

Mitigation

The vendor has addressed this vulnerability in DNN Platform version 10.3.2, as noted in the release notes [1]. Users running versions 9.4.4 or earlier should upgrade to version 10.3.2 or later. The release includes multiple security fixes, including this permissions issue. No workarounds have been documented for unpatched versions.