FortiSandbox - RCE (CVE-2026-39808)

CVE-2026-39808 is a critical OS command injection vulnerability in Fortinet FortiSandbox versions 4.4.0 through 4.4.8 and FortiSandbox PaaS, which allows remote attackers to execute unauthorized code or commands on the affected systems. Exploiting this flaw could enable threat actors to gain full control over the device, potentially leading to data breaches, system compromise, or further attacks within the network.

CrowdSec has been tracking this vulnerability and its exploits since 17th of June 2026.

Insights from the CrowdSec network reveal that the attackers trying to exploit CVE-2026-39808 are composed of a fairly even mix of opportunistic and targeted actors. Some attackers employ preliminary reconnaissance, while others use indiscriminate scanning. Telemetry from the CrowdSec network also shows that exploitation activity for CVE-2026-39808 remains steady week-over-week. Attack volumes are consistent with long-term trends, indicating sustained interest from threat actors. CVE-2026-39808 continues to be an active part of the threat landscape and will likely remain this way for the forseeable future.

Attackers exploit the /fortisandbox/job-detail/tracer-behavior endpoint by injecting OS commands into the jid parameter, enabling unauthorized command execution and file creation on the system. Subsequent requests to /ng/<filename>.txt are used to verify successful exploitation.