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Fencer Vulns
critical 10.0

CVE-2026-28289 in the critical feed json

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

published 2026-03-03 8 mo ago modified 2026-06-17 4 mo ago also EUVD-2026-9347

cvss
10.0
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
35.1%
EPSS 35.1% chance of exploitation in 30 days, percentile 98%
public exploits
1
Metasploit

Summary

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.

Patch / fix

  • freescout freescout 1.8.207

Timeline

  1. First public exploit (Metasploit exploit/multi/http/freescout_htaccess_rce)
  2. Published

CISA SSVC

Exploitation
none
Automatable
yes
Technical impact
total
Assessed
8 mo ago

Exploit prediction

35.10% chance of exploitation in the next 30 days, higher than 98% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • Metasploit exploit/multi/http/freescout_htaccess_rce FreeScout Unauthenticated RCE via ZWSP .htaccess Bypass metasploit exploit, excellent rank, 2026-03-01
  • github.com https://github.com/freescout-help-desk/freescout/security/advisories/GHSA-5gpc-65p8-ffwp referenced PoC, tagged "exploit" by a source, unverified
  • ox.security https://www.ox.security/blog/freescout-rce-cve-2026-28289/ referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 3.1 10.0 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
NVD 3.1 8.1 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H

Affected products

  • freescout-help-desk freescout

Classification

Weakness
  • CWE-434 Unrestricted Upload of File with Dangerous Type

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.