Breaking Down CVE-2026-25089: Unauthenticated Command Injection in FortiSandbox, FortiSandbox Cloud & FortiSandbox PaaS

A critical OS command injection vulnerability, CVE-2026-25089, affects Fortinet FortiSandbox, FortiSandbox Cloud, and FortiSandbox PaaS deployments. The vulnerability allows a remote, unauthenticated attacker to execute arbitrary commands on affected devices by exploiting improper neutralization of special elements used in OS commands within the WEB UI.

A critical OS command injection vulnerability, CVE-2026-25089, affects Fortinet FortiSandbox, FortiSandbox Cloud, and FortiSandbox PaaS deployments. The vulnerability allows a remote, unauthenticated attacker to execute arbitrary commands on affected devices by exploiting improper neutralization of special elements used in OS commands within the WEB UI.

The issue arises when the WEB UI fails to properly sanitize user-supplied input before using it in OS command execution. An attacker can craft a malicious HTTP request containing embedded OS commands that are then executed by the underlying operating system with the privileges of the web server service. As the vulnerability impacts core sandboxing infrastructure, successful exploitation can completely undermine an organization's advanced threat detection capabilities and expose internal networks to unauthorized access.

Vulnerability Details

CVE-2026-25089:
Vulnerability: OS Command Injection (CWE-78)
CVSS Score: 9.8 (Critical)
EPSS Score: 2.03%

The vulnerability stems from improper neutralization of special elements used in an OS command within the FortiSandbox WEB UI.

The WEB UI component fails to properly sanitize user-supplied input in specific HTTP request parameters. Because the input is used to construct a system-level command, an attacker can inject arbitrary commands by embedding them within malicious HTTP requests using operators such as semicolons (;), pipes (|), or command substitution ($()). These injected commands then execute with the privileges of the WEB UI service, often leading to full root or system compromise. Due to the absence of authentication requirements, a remote attacker can exploit this vulnerability without any prior credentials or user interaction.

Infection Method

Step 1: Identify an Exposed FortiSandbox Instance
The attacker scans for internet-facing FortiSandbox, FortiSandbox Cloud, or FortiSandbox PaaS WEB UI instances running a vulnerable version (5.0.0 through 5.0.5, 4.4.0 through 4.4.8, or 4.2.x).

Step 2: Craft a Malicious HTTP Request
The attacker creates a specially crafted HTTP request containing embedded OS commands within a vulnerable parameter, using command injection operators such as semicolons (;), pipes (|), or command substitution ($()).

Step 3: Send the Malicious Request Without Authentication
The crafted request is sent to the target's WEB UI endpoint. The vulnerability requires no prior authentication or user interaction.

Step 4: Command Injection Execution
Because the WEB UI fails to neutralize special elements (CWE-78), the injected commands are passed to the underlying operating system and execute with the privileges of the WEB UI service.

Step 5: Establish Unauthorized Remote Access
The attacker successfully gains remote command execution capabilities on the FortiSandbox appliance without providing any credentials.

Step 6: Access Internal Resources and Perform Further Attacks
After gaining control of the sandbox appliance, the attacker can pivot to internal networks, exfiltrate submitted samples and analysis reports, disable malware detection capabilities, deploy ransomware, recruit the appliance into a botnet, or access sensitive internal systems.

Impact

• Complete System Compromise
• Sandbox Evasion and Blind Spot Creation
• Exposure of Sensitive Threat Intelligence
• Lateral Movement to Internal Networks
• Ransomware Deployment
• Botnet Recruitment
• Credential Harvesting
• Persistent Backdoor Installation

Attack Flow

Initial Access → Identify Exposed FortiSandbox/FortiSandbox Cloud/FortiSandbox PaaS WEB UI → Craft Malicious HTTP Request with OS Commands → Send Request without Authentication → WEB UI Fails to Neutralize Special Elements (CWE-78) → OS Command Execution → Establish Unauthorized Remote Code Execution → Disable Sandbox Detection → Exfiltrate Threat Intelligence → Pivot to Internal Networks → Deploy Ransomware or Botnet → Access Sensitive Systems and Data

Mitigation

• Upgrade affected installations to vendor-fixed versions: FortiSandbox 5.0.x to 5.0.6 or above; FortiSandbox 4.4.x to 4.4.9 or above; FortiSandbox 4.2.x to a fixed version; FortiSandbox Cloud and PaaS 5.0.x to 5.0.6 or above.
• Restrict management access to the WEB UI. As a temporary measure until patching is complete, limit WEB UI access strictly to trusted internal IP ranges via Local-in policies or firewall rules. Do not expose the management interface to the internet.
• Enforce multi-factor authentication (MFA) for all administrative access to FortiSandbox appliances.
• Monitor for indicators of compromise including HTTP requests containing command injection operators (;, |, &, $(), `), web server processes spawning shells, and unexpected outbound connections.
• Implement network segmentation to limit the blast radius of a compromised sandbox appliance.

Instantly Fix Risks with Saner Patch Management

Saner patch management is a continuous, automated, and integrated software that instantly fixes risks exploited in the wild. The software supports major operating systems like Windows, Linux, and macOS, as well as 550+ third-party applications.

It also allows you to set up a safe testing area to test patches before deploying them in a primary production environment. Saner patch management additionally supports a patch rollback feature in case of patch failure or a system malfunction.

Experience the fastest and most accurate patching software here.