CVE-2026-28289
FreeScout 1.8.206 Patch Bypass for CVE-2026-27636 via Zero-Width Space Character Leads to Remote Code Execution
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.
- Affected
- freescout-help-desk · freescout
- CVSS v3.1 NVD
- 8.1 HIGH
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H - CVSS v3.1 GITHUB
- 10.0 CRITICAL
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H - EPSS
- 2.66% chance of exploitation in the next 30 days, 85th percentile
- Published
- 2026-03-03
- Updated
- 2026-03-05
Proof-of-concept exploits (1)
- 0xBlackash/CVE-2026-282891★ · 2026-03-05
Metasploit modules (1)
Security advisories
- freescout-help-desk/freescout/security/advisories/GHSA-5gpc-65p8-ffwp
- https://www.ox.security/blog/freescout-rce-cve-2026-28289
- freescout-help-desk/freescout/commit/f7bc16c56a6b13c06da52ad51fd666546b40818f