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CVE-2026-28289

FreeScout 1.8.206 Patch Bypass for CVE-2026-27636 via Zero-Width Space Character Leads to Remote Code Execution

Published: Mar 3, 2026Updated: Mar 5, 2026 Sources: CVE List NVDCWE-434
NVD MITRE
10.0CVSSCRITICAL
EPSS Score
31.1%
Top 2.0%
CISA KEV
Not in KEV
Exploits
1 Known
Remediation
Patch Available

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.

CVSS Vector Breakdown

AV:NAC:LPR:NUI:NS:CC:HI:HA:H
Exploitability
AV:NAttack Vector
Network
AC:LAttack Complexity
Low
PR:NPrivileges Required
None
UI:NUser Interaction
None
Scope
S:CScope
Changed
Impact
C:HConfidentiality
High
I:HIntegrity
High
A:HAvailability
High
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Weaknesses

CWE-434

Affected Products

freescoutfreescout-help-desk
On-premWeb App
Enterprise Software / itsm-monitoring
freescoutfreescout
Mixed
Enterprise Software / itsm-monitoring
freescout-help-deskcommercialEnterprise Software
freescoutcommercialEnterprise Softwareaka freescout

Attack Graph

Products CVE Techniques Tactics

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Exploitability

1 exploit source identified

Exploit details including PoC links, Metasploit modules, and scanner templates are available after registration.

View exploit details
Official Patch Available
Workaround Available

MITRE ATT&CK

3 techniques
Command and Control
Initial Access
Persistence
View detailed technique mapping

References

https://github.com/freescout-help-desk/freescout/security/advisories/GHSA-5gpc-65p8-ffwp
github.com
https://github.com/freescout-help-desk/freescout/commit/f7bc16c56a6b13c06da52ad51fd666546b40818f
github.com
https://www.ox.security/blog/freescout-rce-cve-2026-28289/
ox.security

Timeline

Published
Mar 3, 2026
Last Updated
Mar 5, 2026

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