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Upgrade to ProDetect Fortinet FortiSandbox OS Command Injection (CVE-2026-39808) in CrowdStrike LogScale
Detects potential exploitation of CVE-2026-39808, an OS command injection vulnerability (CWE-78) in Fortinet FortiSandbox that allows an authenticated or unauthenticated attacker to execute arbitrary OS commands via crafted requests to the FortiSandbox management interface. This vulnerability is listed in CISA's Known Exploited Vulnerabilities (KEV) catalog and is subject to BOD 26-04 remediation timelines. Detection focuses on anomalous shell/command execution patterns originating from FortiSandbox processes, suspicious HTTP requests to the management interface containing shell metacharacters, and unexpected child processes spawned by FortiSandbox web/API services observed via syslog, proxy, or EDR telemetry on adjacent/monitoring hosts.
MITRE ATT&CK
- Tactic
- Initial Access Execution
LogScale Detection Query
#event_simpleName=ProcessRollup2
| in(field="ParentBaseFileName", values=["fsav_httpd", "httpsd", "forticron", "fsw_agent"], ignoreCase=true)
| in(field="FileName", values=["sh", "bash", "wget", "curl", "nc", "chmod", "python", "perl"], ignoreCase=true)
| table(["@timestamp", ComputerName, ParentBaseFileName, FileName, CommandLine])
| sort("@timestamp", order=desc)CrowdStrike CQL query to surface suspicious child process execution (shell, download utilities, interpreters) spawned by FortiSandbox-related service processes, indicating potential post-exploitation of CVE-2026-39808 on a monitored adjacent host or FortiSandbox appliance with EDR coverage.
Data Sources
Required Tables
False Positives & Tuning
- Legitimate administrative scripts or maintenance jobs run by FortiSandbox service accounts
- Scheduled backup or update processes invoking shell utilities
- EDR sensor deployed on a jump host misattributing parent process names
Other platforms for CVE-2026-39808
Testing Methodology
Validate this detection against 3 adversary techniques from Atomic Red Team. Each test below lists the behaviour to exercise and the telemetry you should expect to see. Executable commands and cleanup steps are available with Pro.
- Test 1Simulate command injection payload via HTTP request
Expected signal: Proxy/firewall log entry with RequestURL containing ';id' directed at a lab FortiSandbox API endpoint
- Test 2Simulate reverse-shell download attempt via injected command
Expected signal: Decoded URL parameter containing '&&wget' pattern logged in proxy/CEF logs; potential outbound connection to LAB-C2 in network logs
- Test 3Simulate suspicious child process spawn from FortiSandbox-named parent
Expected signal: EDR process-creation event showing ParentBaseFileName 'fsav_httpd' spawning /bin/bash with CommandLine containing the test string
References (4)
- https://fortiguard.fortinet.com/psirt/FG-IR-26-100
- https://www.cisa.gov/news-events/directives/bod-26-04-prioritizing-security-updates-based-risk
- https://www.cisa.gov/news-events/directives/bod-26-04-implementation-guidance-prioritizing-security-updates-based-risk
- https://nvd.nist.gov/vuln/detail/CVE-2026-39808
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