CVE-2026-28289
CRITICALCVSS Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
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Description
FreeScout is a free help desk and shared inbox built with PHP'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.
Analysis
File upload bypass in FreeScout 1.8.206 — patch bypass for CVE-2026-27636. PoC and patch available. …
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Remediation
Within 24 hours: Inventory all FreeScout instances and assess external accessibility; apply vendor patch immediately to production systems or take affected systems offline if patching is not immediately possible. Within 7 days: Complete patching across all FreeScout deployments and verify patch installation through vulnerability scanning. …
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External POC / Exploit Code
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