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Upgrade to ProDetect Fortinet FortiSandbox OS Command Injection (CVE-2026-39808) in Sumo Logic CSE
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
Sumo Detection Query
_sourceCategory=*fortinet* OR _sourceCategory=*proxy*
| parse regex "(?<url>\S*(api|sys|cgi-bin)\S*)"
| where url matches "*;*" or url matches "*|*" or url matches "*&&*" or url matches "*wget*" or url matches "*curl*" or url matches "*/bin/sh*" or url matches "*/bin/bash*"
| count by url, _sourceHost
| sort -_countSumo Logic search identifying FortiSandbox-related web requests with embedded shell metacharacters or command-execution primitives consistent with exploitation of CVE-2026-39808.
Data Sources
Required Tables
False Positives & Tuning
- Scanner traffic from authorized security assessments
- Non-malicious use of special characters in legitimate API payloads
- Log parsing artifacts misclassifying benign URLs
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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