CVE-2024-21755: Fortinet FortiSandbox RCE Vulnerability

CVE-2024-21755 Overview

CVE-2024-21755 is an operating system (OS) command injection vulnerability affecting Fortinet FortiSandbox appliances. The flaw stems from improper neutralization of special elements in OS commands [CWE-78]. An authenticated attacker can send crafted requests to execute unauthorized code or commands on the underlying system.

The vulnerability affects FortiSandbox versions 4.4.0 through 4.4.3, 4.2.1 through 4.2.6, and 4.0.0 through 4.0.4. Successful exploitation impacts confidentiality, integrity, and availability of the sandbox appliance, which is often positioned as a trust anchor for malware analysis in enterprise environments.

Critical Impact
Authenticated attackers can execute arbitrary OS commands on FortiSandbox appliances over the network, compromising a security control that inspects untrusted files.

Affected Products

Fortinet FortiSandbox 4.4.0 through 4.4.3
Fortinet FortiSandbox 4.2.1 through 4.2.6
Fortinet FortiSandbox 4.0.0 through 4.0.4

Discovery Timeline

2024-04-09 - CVE-2024-21755 published to NVD
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2024-21755

Vulnerability Analysis

CVE-2024-21755 is classified as OS command injection under CWE-78. The FortiSandbox management interface fails to properly neutralize shell metacharacters supplied through crafted requests. When these unsanitized values reach a system call, the appliance executes attacker-controlled commands with the privileges of the invoking process.

Exploitation requires network access to the FortiSandbox interface and low-privilege authentication. Once achieved, the attacker gains command execution on a device that typically holds sensitive sample data, network telemetry, and analyst credentials. This creates a pivot point deeper into the security operations infrastructure.

At publication, no public proof-of-concept exploit is listed and the CVE is not present on the CISA Known Exploited Vulnerabilities catalog. The EPSS score of 2.48% (83rd percentile) indicates elevated exploitation likelihood relative to the broader CVE population.

Root Cause

The root cause is missing or insufficient input sanitization on parameters that are later concatenated into shell command strings. Special characters such as ;, |, `, $(), and && are not stripped or escaped before invocation, allowing command chaining.

Attack Vector

The attack vector is network-based against the FortiSandbox management surface. An attacker with valid low-privilege credentials submits a request containing shell metacharacters embedded in a vulnerable parameter. The appliance interprets the payload as additional commands, yielding arbitrary execution. Refer to the FortiGuard Security Advisory FG-IR-23-489 for vendor-supplied details.

Detection Methods for CVE-2024-21755

Indicators of Compromise

Unexpected outbound connections originating from the FortiSandbox management interface to unknown hosts.
Anomalous child processes spawned by FortiSandbox web or API service accounts, particularly shells such as /bin/sh or /bin/bash.
New or modified files in system directories, cron entries, or SSH authorized_keys on the appliance.
Authentication events from unusual source IPs immediately followed by administrative API calls.

Detection Strategies

Inspect FortiSandbox HTTP/API request logs for shell metacharacters (;, |, `, $(, &&) in parameter values.
Correlate authenticated sessions with subsequent configuration or job-execution requests that deviate from analyst baselines.
Compare running services and process trees against a known-good FortiSandbox baseline for the deployed firmware version.

Monitoring Recommendations

Forward FortiSandbox syslog and admin audit logs to a centralized SIEM for retention and correlation.
Alert on failed-then-successful login sequences against the FortiSandbox administrative interface.
Monitor egress traffic from the appliance segment; sandbox devices should have tightly scoped outbound flows.

How to Mitigate CVE-2024-21755

Immediate Actions Required

Upgrade FortiSandbox to a fixed release as directed in FortiGuard advisory FG-IR-23-489.
Restrict network reachability to the FortiSandbox management interface to trusted administrative subnets only.
Rotate credentials for all FortiSandbox local and remote administrator accounts.
Review audit logs for signs of exploitation dating back to the earliest affected release in your environment.

Patch Information

Fortinet has released fixed builds beyond the vulnerable ranges. Administrators should move off FortiSandbox 4.4.0–4.4.3, 4.2.1–4.2.6, and 4.0.0–4.0.4 to a version listed as remediated in the FortiGuard advisory. Validate the upgrade path through Fortinet's documented compatibility matrix.

Workarounds

Limit administrative access to the FortiSandbox web interface using network access control lists.
Enforce multi-factor authentication for all administrative accounts to raise the bar for the required authenticated session.
Disable or restrict low-privilege accounts that are not required for daily operations until patching is complete.

bash

# Configuration example: restrict FortiSandbox admin access to trusted networks
config system interface
  edit port1
    set allowaccess https ssh
    set trusthost1 10.0.10.0 255.255.255.0
  next
end