CVE-2026-28289— FreeScout 1.8.206 Patch Bypass for CVE-2026-27636 via Zero-Width Space Character Leads to Remote Code Execution
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I. Basic Information for CVE-2026-28289
Vulnerability Information
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Vulnerability Title
FreeScout 1.8.206 Patch Bypass for CVE-2026-27636 via Zero-Width Space Character Leads to Remote Code Execution
Source: NVD (National Vulnerability Database)
Vulnerability 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.
Source: NVD (National Vulnerability Database)
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
Source: NVD (National Vulnerability Database)
Vulnerability Type
危险类型文件的不加限制上传
Source: NVD (National Vulnerability Database)
Vulnerability Title
FreeScout 代码问题漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
FreeScout是FreeScout公司的一个使用 PHP（Laravel 框架）构建的超轻量级且功能强大的免费开源帮助台和共享收件箱。 FreeScout 1.8.206及之前版本存在代码问题漏洞，该漏洞源于sanitizeUploadedFileName函数存在TOCTOU缺陷，可能导致具有文件上传权限的已验证用户通过上传恶意.htaccess文件实现远程代码执行。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)
Shenlong Deep Dive — AI Deep Analysis
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Affected Products
| Vendor | Product | Affected Versions | CPE | Subscribe |
|---|---|---|---|---|
| freescout-help-desk | freescout | < 1.8.207 | - |
II. Public POCs for CVE-2026-28289
| # | POC Description | Source Link | Shenlong Link |
|---|
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IV. Related Vulnerabilities
Same product: freescout
- CVE-2026-41906
FreeScout: Conversation Change-Customer Cross-Mailbox Author - CVE-2026-41905
FreeScout vulnerable to SSRF via Helper::sanitizeRemoteUrl: - CVE-2026-41904
FreeScout Stored XSS vulnerability in mailbox auto-reply: pa - CVE-2026-41902
FreeScout's user invitation hash never expires: permanent un - CVE-2026-41903
FreeScout IDOR Vulnerability: PERM_EDIT_USERS allows modifyi
Same vendor: freescout-help-desk
- CVE-2026-41906
FreeScout: Conversation Change-Customer Cross-Mailbox Author - CVE-2026-41905
FreeScout vulnerable to SSRF via Helper::sanitizeRemoteUrl: - CVE-2026-41904
FreeScout Stored XSS vulnerability in mailbox auto-reply: pa - CVE-2026-41902
FreeScout's user invitation hash never expires: permanent un - CVE-2026-41903
FreeScout IDOR Vulnerability: PERM_EDIT_USERS allows modifyi
Same weakness: CWE-434
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TextPattern CMS 4.8.7 Remote Code Execution via File Upload - CVE-2021-47937
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Emlog: Remote Code Execution via Malicious Plugin Upload - CVE-2026-6692
Slider Revolution 7.0.0 - 7.0.10 - Authenticated (Subscriber - CVE-2026-41587
CI4MS: Unrestricted PHP File Upload via Theme Installation L
V. Comments for CVE-2026-28289
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