CVE-2024-21756 Overview
CVE-2024-21756 is an OS command injection vulnerability [CWE-78] affecting multiple versions of Fortinet FortiSandbox. The flaw allows an authenticated remote attacker to execute unauthorized code or commands by sending crafted requests to the appliance. The vulnerability stems from improper neutralization of special elements passed to underlying operating system commands.
Critical Impact
Successful exploitation grants an attacker command execution on the FortiSandbox appliance, compromising the confidentiality, integrity, and availability of the malware analysis platform and any samples it processes.
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-2024-21756 published to the National Vulnerability Database
- 2026-06-17 - Last updated in NVD database
Technical Details for CVE-2024-21756
Vulnerability Analysis
CVE-2024-21756 is classified as an OS command injection weakness under [CWE-78]. FortiSandbox exposes network-reachable functionality that constructs operating system commands using attacker-influenced input. Because special shell metacharacters are not properly neutralized before the command is passed to the underlying shell, an attacker can append or inject additional commands.
The attack requires low privileges and no user interaction, and it is exploitable over the network. Successful exploitation results in arbitrary command execution in the context of the FortiSandbox process, which typically runs with elevated privileges on the appliance.
Because FortiSandbox is a malware detonation platform, compromise of the appliance can undermine detection logic, expose analyzed samples and verdicts, and provide a pivot point deeper into the security stack.
Root Cause
The root cause is missing or insufficient input sanitization when user-supplied data is incorporated into an operating system command string. Special characters such as ;, &, |, backticks, and $() are not filtered or escaped, allowing shell interpretation of injected payloads.
Attack Vector
An authenticated attacker sends crafted HTTP or management-plane requests containing shell metacharacters in fields that are ultimately reflected into a system-level command. The attacker leverages this to append arbitrary commands, which the appliance then executes. See the FortiGuard Security Advisory FG-IR-23-489 for vendor guidance.
No public proof-of-concept exploit or CISA KEV listing exists for this issue at the time of writing. The EPSS score indicates a moderate probability of exploitation activity relative to the broader CVE population.
Detection Methods for CVE-2024-21756
Indicators of Compromise
- Unexpected child processes spawned by FortiSandbox web or management daemons, especially shells such as sh, bash, or utilities like curl, wget, nc.
- Outbound network connections from the FortiSandbox appliance to unknown or non-Fortinet infrastructure.
- New or modified files in system paths outside of normal update activity, and unexpected cron entries.
- Authenticated administrative sessions from unusual source addresses preceding anomalous appliance behavior.
Detection Strategies
- Inspect FortiSandbox web and audit logs for request parameters containing shell metacharacters such as ;, &&, |, `, or $().
- Correlate authenticated API and GUI activity with subsequent outbound connections or configuration changes on the appliance.
- Alert on any deviation from the baseline of processes and network flows expected from a FortiSandbox device.
Monitoring Recommendations
- Forward FortiSandbox syslog and audit events to a centralized SIEM for long-term analysis and correlation with adjacent Fortinet devices.
- Monitor administrative account usage and enforce alerting on privilege changes, new admin accounts, or credential resets.
- Track appliance software version and patch status continuously to detect drift from a known-good baseline.
How to Mitigate CVE-2024-21756
Immediate Actions Required
- Upgrade FortiSandbox to a fixed release as documented in FortiGuard advisory FG-IR-23-489.
- Restrict management-plane access to trusted administrative networks and jump hosts only.
- Rotate all administrative credentials and API tokens used with the appliance after patching.
- Review recent audit logs for signs of exploitation prior to remediation.
Patch Information
Fortinet has released fixed builds for the affected FortiSandbox branches. Consult the FortiGuard Security Advisory FG-IR-23-489 for the specific fixed versions corresponding to 4.4.x, 4.2.x, and 4.0.x, and follow Fortinet's upgrade path guidance for your current release.
Workarounds
- Limit access to the FortiSandbox management interface using network ACLs, firewall policies, and out-of-band management VLANs.
- Enforce strong, unique administrative credentials and enable multi-factor authentication for all admin accounts.
- Reduce the number of privileged accounts on the appliance to the minimum required for operations.
# Example: restrict FortiSandbox management access at the network edge
# Only allow the admin jump host to reach the FortiSandbox GUI/API
access-list FSA_MGMT permit tcp host 10.10.10.5 host 10.20.30.40 eq 443
access-list FSA_MGMT deny tcp any host 10.20.30.40 eq 443
access-list FSA_MGMT permit ip any any
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
