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Upgrade to ProDetect Fortinet FortiSandbox OS Command Injection (CVE-2026-25089) in Google Chronicle
Detects potential exploitation of CVE-2026-25089, an OS command injection vulnerability (CWE-78) in Fortinet FortiSandbox that allows an authenticated or remote attacker to execute arbitrary commands on the underlying operating system via crafted input to a vulnerable API/web endpoint. This vulnerability is listed in the CISA Known Exploited Vulnerabilities (KEV) catalog and is subject to BOD 26-04 prioritized remediation timelines. Detection focuses on anomalous shell/process execution spawned from FortiSandbox web/management processes, suspicious HTTP requests containing shell metacharacters against FortiSandbox management interfaces, and post-exploitation command execution artifacts.
MITRE ATT&CK
YARA-L Detection Query
rule fortisandbox_cmd_injection_cve_2026_25089 {
meta:
author = "df00tech"
description = "Detects potential OS command injection exploitation attempts against Fortinet FortiSandbox (CVE-2026-25089)"
severity = "CRITICAL"
reference = "https://fortiguard.fortinet.com/psirt/FG-IR-26-141"
events:
$e.metadata.event_type = "NETWORK_HTTP"
$e.target.application = "FortiSandbox"
re.regex($e.network.http.request_url, `(;|\||&&|\$\(|` + "`" + `|wget |curl |chmod \+x|/bin/sh|/bin/bash)`)
condition:
$e
}YARA-L rule matching HTTP requests to FortiSandbox containing shell metacharacters or command-injection fragments consistent with CVE-2026-25089 exploitation.
Data Sources
Required Tables
False Positives & Tuning
- UDM-normalized logs from authorized vulnerability scans
- Legitimate encoded parameters misclassified as suspicious due to shared characters
- Log parser artifacts introducing metacharacters into normalized URL fields
Other platforms for CVE-2026-25089
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 in HTTP request
Expected signal: HTTP access log entry on the FortiSandbox lab appliance (or reverse proxy) showing the request URL with embedded shell metacharacters
- Test 2Simulate payload download via wget from web-server-spawned shell
Expected signal: Process creation event showing wget spawned as a child of a web-server user/process, with associated CommandLine and ParentBaseFileName
- Test 3Simulate reverse shell command execution pattern
Expected signal: Process creation log/EDR telemetry showing sh -c invocation with an unusual parent process (web server user context)
References (4)
- https://fortiguard.fortinet.com/psirt/FG-IR-26-141
- 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-2026-25089
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