CVE-2026-27636
Published: 25 February 2026
Summary
CVE-2026-27636 is a high-severity Unrestricted Upload of File with Dangerous Type (CWE-434) vulnerability in Freescout Freescout. Its CVSS base score is 8.8 (High).
Operationally, exploitation aligns with the MITRE ATT&CK technique Exploit Public-Facing Application (T1190); ranked in the top 20.5% of CVEs by exploit likelihood; it is not currently listed in the CISA KEV catalog; a public proof-of-concept is referenced.
The strongest mitigations our analysis identified are NIST 800-53 SI-10 (Information Input Validation) and SI-2 (Flaw Remediation).
Deeper analysis
CVE-2026-27636 is an unrestricted upload vulnerability in FreeScout, an open-source help desk and shared inbox application built on PHP's Laravel framework. In versions prior to 1.8.206, the file upload restriction list implemented in `app/Misc/Helper.php` fails to block `.htaccess` or `.user.ini` files. This allows authenticated users to upload such files to directories on Apache web servers configured with `AllowOverride All`, a common default setting, enabling attackers to override server configurations for malicious purposes. The vulnerability carries a CVSS v3.1 base score of 8.8 (AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H) and is associated with CWE-434 (Unrestricted Upload of File with Dangerous Type).
An authenticated user with low privileges, such as a standard help desk ticket submitter, can exploit this remotely over the network with low complexity and no user interaction required. By uploading a crafted `.htaccess` file, the attacker redefines how Apache processes subsequent files, leading to remote code execution (RCE) on the server. This can occur independently or in combination with CVE-2026-27637, potentially granting full server compromise including data exfiltration, privilege escalation, or further lateral movement.
The FreeScout project addressed this in version 1.8.206 by updating the file upload restrictions in `app/Misc/Helper.php` to explicitly block `.htaccess` and `.user.ini` files, as detailed in the project's GitHub security advisories (GHSA-6gcm-v8xf-j9v9 and GHSA-mw88-x7j3-74vc) and the fixing commit (9984071e6f1b4e633fdcffcea82bbebc9c1e009c). Security practitioners should upgrade to 1.8.206 or later, review Apache configurations to limit `AllowOverride` where possible, and audit file upload directories for unauthorized `.htaccess` files.
OWASP Top 10 for Web (2025)
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-8612
Vulnerability details
FreeScout is a free help desk and shared inbox built with PHP's Laravel framework. Prior to version 1.8.206, FreeScout's file upload restriction list in `app/Misc/Helper.php` does not include `.htaccess` or `.user.ini` files. On Apache servers with `AllowOverride All` (a common…
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configuration), an authenticated user can upload a `.htaccess` file to redefine how files are processed, enabling Remote Code Execution. This vulnerability can be exploited on its own or in combination with CVE-2026-27637. Version 1.8.206 fixes both vulnerabilities.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise TechniquesAI
Why these techniques?
Unrestricted file upload vulnerability in public-facing web application (FreeScout) enables authenticated attackers to upload .htaccess files for remote code execution by overriding Apache configurations.
CVEs Like This One
Affected Assets
Mitigating Controls
Mitigating Controls (NIST 800-53 r5) AI
Directly enforces restrictions on file upload inputs by blocking dangerous types like .htaccess and .user.ini omitted from FreeScout's restriction list.
Implements input validation mechanisms at file upload points to reject unrestricted uploads of server configuration files enabling RCE.
Requires timely remediation of the specific application flaw via patching, as done in FreeScout 1.8.206 to update the upload blacklist.