CVE-2026-28289

Severity CVSS v4.0:

Pending analysis

Type:

CWE-434 Unrestricted Upload of File with Dangerous Type

Publication date:

03/03/2026

Last modified:

11/03/2026

Description

FreeScout is a free help desk and shared inbox built with PHP&#39;s Laravel framework. A patch bypass vulnerability for CVE-2026-27636 in FreeScout 1.8.206 and earlier allows any authenticated user with file upload permissions to achieve Remote Code Execution (RCE) on the server by uploading a malicious .htaccess file using a zero-width space character prefix to bypass the security check. The vulnerability exists in the sanitizeUploadedFileName() function in app/Http/Helper.php. The function contains a Time-of-Check to Time-of-Use (TOCTOU) flaw where the dot-prefix check occurs before sanitization removes invisible characters. This vulnerability is fixed in 1.8.207.

Impact

Vector 3.x

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H CVSS v3.1 Severity and Metrics:

Base Score: 10.00 CRITICAL
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H

Attack Vector (AV): Network
Attack Complexity (AC): Low
Privileges Required (PR): None
User Interaction (UI): None
Scope (S): Changed
Confidentiality (C): High
Integrity (I): High
Availability (A): High