Fortinet FortiWeb cat_cgi_paths Out-Of-Bounds Write Remote Code Execution Vulnerability

April 15th, 2026
ZDI-26-266 ZDI-CAN-28661

CVE ID

CVE-2026-40688

CVSS Score

8.8 AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Affected Vendors

Fortinet

Affected Products

FortiWeb

Vulnerability Details

This vulnerability allows remote attackers to execute arbitrary code on affected installations of Fortinet FortiWeb. Authentication is required to exploit this vulnerability.

The specific flaw exists within the handling of HTTP requests. The issue results from the lack of proper validation of user-supplied data, which can result in a write past the end of an allocated buffer. An attacker can leverage this vulnerability to execute code in the context of root.

Additional Details

Fortinet has issued an update to correct this vulnerability. More details can be found at:
https://fortiguard.fortinet.com/psirt/FG-IR-26-127

Disclosure Timeline

  • 2025-12-09 - Vulnerability reported to vendor
  • 2026-04-15 - Coordinated public release of advisory
  • 2026-04-15 - Advisory Updated

Credit

Jason McFadyen of Trend Research

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