Two critical FortiSandbox command injection vulnerabilities: CVE-2026-25089 and CVE-2026-39808 were added to the CISA Known Exploited Vulnerabilities catalog on July 16, 2026. Both carry CVSS 9.1 and 9.8 scores respectively, allow unauthenticated remote code execution as root, and now have a federal patch deadline of July 19, 2026. A public proof-of-concept exploit for CVE-2026-39808 demonstrates trivial exploitation via a single curl command.

Vulnerability Details

CVE-2026-25089 (CVSS 9.1 Critical)

• Type: OS Command Injection (CWE-78)
• Attack Vector: Network, unauthenticated
• Impact: Unauthorized command execution via crafted HTTP requests
• Affected Products:
  • FortiSandbox 5.0.0 through 5.0.5
  • FortiSandbox 4.4.0 through 4.4.8
  • FortiSandbox 4.2 all versions
  • FortiSandbox Cloud 5.0.4 through 5.0.5
  • FortiSandbox PaaS 5.0.4 through 5.0.5
• CISA KEV Entry: July 16, 2026
• Vendor Advisory: FG-IR-26-141

CVE-2026-39808 (CVSS 9.8 Critical)

• Type: OS Command Injection (CWE-78)
• Attack Vector: Network, unauthenticated
• Impact: Unauthorized command execution as root via crafted HTTP requests
• Affected Products:
  • FortiSandbox 4.4.0 through 4.4.8
  • FortiSandbox PaaS versions 21.3.4055 through 23.4.4374
• CISA KEV Entry: July 16, 2026
• Vendor Advisory: FG-IR-26-100
• Public PoC: GitHub repository samu-delucas/CVE-2026-39808
• CISA SSVC Status: Updated from "poc" to "active" exploitation on July 16

Both vulnerabilities share the same CVSS 3.1 vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H — network attack vector, low complexity, no privileges required, no user interaction, with high impact on confidentiality, integrity, and availability.

Impact Assessment

FortiSandbox is Fortinet's advanced threat protection appliance that analyzes suspicious files and URLs in a sandboxed environment. It is widely deployed in enterprise networks, often with direct internet exposure for email and web traffic analysis.

What's at risk:

• Full appliance compromise: Both vulnerabilities allow unauthenticated attackers to execute arbitrary commands as root
• Network pivot: Compromised sandboxes sit deep in security infrastructure, providing lateral movement paths
• Data exfiltration: Access to analyzed malware samples, network traffic captures, and threat intelligence
• Persistence: Root access enables firmware modification, backdoor installation, and log tampering
• Supply chain risk: FortiSandbox Cloud and PaaS variants extend the attack surface to managed service providers

The CISA KEV listing confirms active exploitation in the wild. The three-day remediation window (July 16-19) under Binding Operational Directive 26-04 reflects the severity: federal agencies must patch or disconnect by July 19, and private sector organizations should treat this with equal urgency.

Affected Systems: Who Needs to Act

Any organization running the following should assume immediate risk:

Product	Affected Versions	Fixed Version
FortiSandbox	5.0.0 - 5.0.5	5.0.6+
FortiSandbox	4.4.0 - 4.4.8	4.4.9+
FortiSandbox	4.2 all versions	Upgrade to 4.4.9+ or 5.0.6+
FortiSandbox Cloud	5.0.4 - 5.0.5	5.0.6+ (managed by Fortinet)
FortiSandbox PaaS	5.0.4 - 5.0.5	5.0.6+ (managed by Fortinet)
FortiSandbox PaaS	21.3.4055 - 23.4.4374	Check FG-IR-26-100 for version mapping

Critical note: FortiSandbox 4.2 has no patched version in the 4.2 branch: organizations on 4.2 must upgrade to 4.4.9+ or 5.0.6+.

Mitigation and Patching: Step-by-Step Fix

Immediate Actions (Do Today)

1. Apply vendor patches immediately

   • Download firmware from Fortinet Support (requires valid contract)
   • FortiSandbox 5.0.6, 4.4.9 address both CVEs
   • FortiSandbox Cloud and PaaS: Fortinet applies patches automatically; verify with your account team

2. If patching is not immediately possible:

   • Restrict management interface access to trusted IPs only
   • Block internet-facing access to /fortisandbox/job-detail/tracer-behavior endpoint
   • Implement WAF rules to filter pipe (|) and command injection patterns in HTTP parameters
   • Monitor for anomalous outbound connections from sandbox appliances

3. Verify patch application

   • Check firmware version post-upgrade: get system status
   • Confirm no unexpected processes: diagnose sys process list
   • Review logs for exploitation attempts: diagnose log device and filter for tracer-behavior

Detection Rules

Suricata / Snort rule for CVE-2026-39808 exploitation:

alert http any any -> any any ( msg:"EXPLOIT FortiSandbox CVE-2026-39808 Command Injection Attempt"; flow:established,to_server; http.uri; content:"/fortisandbox/job-detail/tracer-behavior"; http.client_body; pcre:"/jid.*[\|;].*(id|whoami|cat|wget|curl|bash)/i"; classtype:attempted-admin; sid:202639808; rev:1; metadata:cve,2026-39808; )

YARA rule for post-exploitation artifacts:

Log query for Splunk / Elastic:

Frequently Asked Questions

Is CVE-2026-39808 actively exploited?

Yes. The CISA KEV listing confirms active exploitation. A public PoC on GitHub demonstrates unauthenticated RCE as root via a single curl command targeting the jid parameter.

Does CVE-2026-25089 have a public exploit?

As of July 17, 2026, no public PoC is available for CVE-2026-25089. However, the CISA KEV entry indicates it is being exploited in the wild. Assume weaponized exploits exist.

Are FortiSandbox Cloud and PaaS customers protected?

Fortinet manages patching for Cloud and PaaS offerings. However, CISA KEV includes both products, suggesting the patches may not yet be fully deployed or that customer-configurable components remain vulnerable. Contact Fortinet support to confirm your instance status.

What if I am on FortiSandbox 4.2?

There is no 4.2.x patch. You must upgrade to 4.4.9+ or 5.0.6+. Plan an emergency maintenance window: this is not optional.

Can I mitigate without patching?

Partial mitigation is possible by restricting network access to the management interface and the vulnerable endpoint. However, command injection vulnerabilities are notoriously difficult to fully block with WAF rules alone. Patching is the only reliable fix.

How do I know if I am already compromised?

• Check for unexpected files in /web/ng/ (the PoC writes output here)
• Review diagnose sys process list for unfamiliar processes running as root
• Inspect tracer-behavior access logs for pipe characters in the jid parameter
• Monitor for outbound connections to unknown IPs from the sandbox appliance
• Run the YARA rule above against the appliance filesystem

Key Takeaways

1. Two critical FortiSandbox RCEs are now in CISA KEV with a July 19, 2026 federal deadline: treat this as an emergency patch cycle
2. CVE-2026-39808 has a public PoC: exploitation is trivial: one curl command achieves root RCE without authentication
3. FortiSandbox 4.2 has no patch: upgrade to 4.4.9+ or 5.0.6+ immediately
4. Cloud and PaaS variants are affected: verify patch status with Fortinet even for managed services
5. Detection is straightforward: the tracer-behavior endpoint and jid parameter are clear IOCs: deploy the Suricata/YARA rules above
6. Network segmentation matters: sandboxes should never have direct internet exposure: this incident reinforces that principle

Conclusion

The dual FortiSandbox command injection vulnerabilities represent a worst-case scenario for security infrastructure: critical appliances designed to protect the network become the entry point. With CVSS 9.1/9.8 scores, unauthenticated root RCE, active exploitation confirmed by CISA, and a public proof-of-concept for one of them, there is no justification for delay.

Organizations running FortiSandbox should patch today: not by the July 19 deadline, but immediately. The three-day CISA window is a regulatory minimum: the practical window for safety closed when the PoC was published.

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Sources:

• CISA Known Exploited Vulnerabilities Catalog: CVE-2026-25089, CVE-2026-39808 (added 2026-07-16)
• NVD: CVE-2026-25089, CVE-2026-39808
• FortiGuard PSIRT: FG-IR-26-141, FG-IR-26-100
• GitHub PoC: samu-delucas/CVE-2026-39808
• CISA BOD 26-04: Prioritizing Security Updates Based on Risk