CVE-2026-25089

Fortinet FortiSandbox OS Command Injection (CVE-2026-25089)

Execution Initial Access Lateral Movement Last updated:

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.

Vulnerability Intelligence

KEV — Known Exploited

Affected Software

Vendor
Fortinet
Product
FortiSandbox

Weakness (CWE)

CWE-78

Timeline

Disclosed
July 16, 2026

CVSS

Unscored
CVSS vector not yet published
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What is CVE-2026-25089 Fortinet FortiSandbox OS Command Injection (CVE-2026-25089)?

Fortinet FortiSandbox OS Command Injection (CVE-2026-25089) (CVE-2026-25089) maps to the Execution and Initial Access and Lateral Movement tactics — the adversary is trying to run malicious code in MITRE ATT&CK.

This page provides production-ready detection logic for Fortinet FortiSandbox OS Command Injection (CVE-2026-25089), covering the data sources and telemetry it touches: CommonSecurityLog, Syslog, AzureFirewall. The queries below are rated critical severity at medium confidence, and ship for 7 SIEM platforms — KQL, SPL, Elastic, QRadar, Sumo, YARA-L, LogScale.

MITRE ATT&CK

Tactic
Execution Initial Access Lateral Movement
Microsoft Sentinel / Defender
kusto 
// Requires firewall/network device logs or FortiSandbox syslog forwarded via CEF/Syslog connector into a custom table (FortiSandboxCL) or CommonSecurityLog
let susPatterns = dynamic([";", "|", "&&", "$(", "`", "wget ", "curl ", "/bin/sh", "/bin/bash", "nc ", "chmod +x"]);
CommonSecurityLog
| where DeviceVendor == "Fortinet" and DeviceProduct has "FortiSandbox"
| where isnotempty(RequestURL) or isnotempty(Message)
| extend RawContent = strcat(tostring(RequestURL), " ", tostring(Message))
| where susPatterns has_any (RawContent)
| extend MatchedPattern = extract_all(@"(;|\||&&|\$\(|`|wget |curl |/bin/sh|/bin/bash|nc |chmod \+x)", RawContent)
| project TimeGenerated, DeviceVendor, DeviceProduct, SourceIP, DestinationIP, RequestURL, Message, MatchedPattern
| sort by TimeGenerated desc

Detects HTTP requests or syslog messages to/from FortiSandbox devices containing shell metacharacters or common command-injection payload fragments consistent with CVE-2026-25089 exploitation attempts.

critical severity medium confidence

Data Sources

CommonSecurityLog Syslog AzureFirewall

Required Tables

CommonSecurityLog Syslog

False Positives

  • Legitimate administrative scripts that pass URL-encoded special characters as part of normal configuration tasks
  • Security scanners/vulnerability assessment tools performing authorized testing against FortiSandbox
  • Third-party integrations pushing crafted payloads for legitimate file analysis submissions

Sigma rule & cross-platform mapping

The detection logic for Fortinet FortiSandbox OS Command Injection (CVE-2026-25089) (CVE-2026-25089) above is provided in a vendor-neutral form so you can deploy it on any SIEM. The same logic is shipped here as native KQL (Microsoft Sentinel / Defender), SPL (Splunk), Elastic (Elastic Security (EQL)), QRadar (IBM QRadar (AQL)), Sumo (Sumo Logic CSE), YARA-L (Google Chronicle / SecOps), LogScale (CrowdStrike LogScale (CQL)) queries. In Sigma terms, this detection targets the following logsource: 

logsource:
  category: network_connection
  product: windows

Browse the community-maintained Sigma rules for this technique:

SigmaHQ rules for CVE-2026-25089 Sigma rules on detection.fyi

Platform-specific guides for CVE-2026-25089

Detect in Microsoft Sentinel (KQL) Detect in Splunk (SPL) Detect in Elastic Security (Elastic) Detect in IBM QRadar (QRadar) Detect in Sumo Logic CSE (Sumo) Detect in Google Chronicle (YARA-L) Detect in CrowdStrike LogScale (LogScale)
Last updated: 2026-07-17 Research depth: standard
References (4)

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.

  1. 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

  2. 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

  3. 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)

Response Playbook

Triage

  1. Confirm the affected FortiSandbox appliance's firmware version against Fortinet's advisory FG-IR-26-141 to determine if it falls within the vulnerable version range
  2. Review FortiSandbox system logs, web access logs, and CLI audit logs around the alert timeframe for unexpected process spawns, shell invocations, or configuration changes
  3. Correlate source IP addresses of suspicious requests against known scanning infrastructure, threat intelligence feeds, and prior authorized testing schedules to rule out false positives
  4. Check for outbound connections from the FortiSandbox device to unfamiliar external IPs/domains that could indicate a reverse shell or payload download following successful injection

Containment

  1. Isolate the FortiSandbox appliance from untrusted network segments (restrict management interface access to trusted admin subnets only) while investigation proceeds
  2. If compromise is confirmed, take the device offline or place it in a quarantined VLAN, then follow Fortinet's guidance to apply the patched firmware version referenced in FG-IR-26-141

Evidence Collection

  1. Export FortiSandbox system event logs, web server access logs, and CLI history covering at least 30 days prior to the earliest detected suspicious activity
  2. Capture a forensic image or configuration/system snapshot of the appliance (where supported) prior to remediation, and preserve any identified dropped files, cron entries, or unauthorized accounts

Escalation Criteria

  • ! Evidence of successful command execution (e.g., new unauthorized system accounts, modified cron jobs, unexpected outbound C2-like traffic, or webshell files) warrants immediate escalation to incident response
  • ! Presence of this device in a network segment with access to sensitive file analysis results, malware samples, or other security tooling should trigger escalation given potential lateral movement risk and the KEV/BOD 26-04 mandated urgency

Investigation Guide

Forensic Artifacts

  • > FortiSandbox web/API access logs showing crafted requests with shell metacharacters
  • > Unexpected child processes (sh, bash, wget, curl) spawned from FortiSandbox web/management daemons
  • > New or modified cron jobs, startup scripts, or unauthorized local/system accounts on the appliance
  • > Outbound network connections from the FortiSandbox device to unfamiliar external hosts

Tuning Guidance

Baseline normal administrative and integration traffic to FortiSandbox management interfaces to reduce noise from legitimate encoded URL parameters. Exclude known vulnerability scanner IP ranges used for authorized assessments. If FortiSandbox logs are not natively ingested, prioritize onboarding syslog/CEF forwarding from the appliance before relying on this detection, and consider raising confidence to high once verified log field mappings are validated in your environment.

Hunting Queries

Broader hunt for command-execution indicators in FortiSandbox logs over a 30-day window to identify low-and-slow or previously unalerted exploitation attempts.

Hunting — KQL
kql 
CommonSecurityLog
| where DeviceProduct has "FortiSandbox"
| where Message has_any ("wget", "curl", "chmod +x", "/bin/sh", "/bin/bash")
| summarize count() by SourceIP, DestinationIP, bin(TimeGenerated, 1h)
| sort by count_ desc
Hunting — SPL
spl 
index=network sourcetype=fortinet:fortisandbox ("wget" OR "curl" OR "chmod +x" OR "/bin/sh" OR "/bin/bash")
| stats count by src_ip, dest_ip, _time
| sort -count

Atomic Red Team Tests

Test 1 Simulate command injection payload in HTTP request
linux

Sends a crafted HTTP request containing shell metacharacters to a lab FortiSandbox instance or mock endpoint to validate log capture and detection logic.

Command

bash 
curl -sk "https://LAB-FORTISANDBOX-IP/api/v1/submit?file=test;id;whoami" -o /dev/null

Cleanup

bash 
No persistent changes made; verify no unintended command execution occurred on the lab target.

Expected Telemetry

HTTP access log entry on the FortiSandbox lab appliance (or reverse proxy) showing the request URL with embedded shell metacharacters

Expected Detection

SIEM alert fires from the kql/spl/elastic_eql rules matching shell metacharacter patterns in the request URL

Test 2 Simulate payload download via wget from web-server-spawned shell
linux

Emulates post-exploitation behavior by having a process resembling the FortiSandbox web daemon spawn wget to fetch a benign test file, validating EDR process-lineage detection.

Command

bash 
sudo -u www-data bash -c 'wget -q http://127.0.0.1:8000/testfile.txt -O /tmp/atomic_test_download.txt'

Cleanup

bash 
rm -f /tmp/atomic_test_download.txt

Expected Telemetry

Process creation event showing wget spawned as a child of a web-server user/process, with associated CommandLine and ParentBaseFileName

Expected Detection

CrowdStrike CQL query flags the wget child process spawned from a web-server-context parent

Test 3 Simulate reverse shell command execution pattern
linux

Generates a benign local process chain resembling a shell invocation (sh -c) launched from a web-server-owned account to validate detection of interpreter execution consistent with command injection.

Command

bash 
sudo -u www-data sh -c 'echo atomic_test_marker > /tmp/atomic_test_marker.txt'

Cleanup

bash 
rm -f /tmp/atomic_test_marker.txt

Expected Telemetry

Process creation log/EDR telemetry showing sh -c invocation with an unusual parent process (web server user context)

Expected Detection

CrowdStrike CQL and Elastic EQL rules identify the shell interpreter execution originating from a web-server-associated parent process

Related Detections

Tactic Hubs

TA0002ExecutionTA0001Initial AccessTA0008Lateral Movement

Related Techniques

T1190Exploit Public-Facing ApplicationT1059Command and Scripting InterpreterT1105Ingress Tool Transfer

Same Tactic: Execution

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