CVE-2026-25089: Fortinet FortiSandbox OS Command Injection Vulnerability

Overview

CVE-2026-25089 is a critical OS command injection vulnerability affecting Fortinet FortiSandbox, FortiSandbox Cloud, and FortiSandbox PaaS. This flaw allows unauthenticated attackers to execute arbitrary commands on the underlying system by sending specially crafted HTTP requests. Given its high severity (CVSS 9.8) and confirmed active exploitation, organizations utilizing affected FortiSandbox products are at immediate risk of compromise.

Technical Analysis

• Vulnerability: Improper neutralization of special elements used in an OS command (‘OS Command Injection’) (CWE-78).
• Impact: Unauthenticated remote code execution (RCE).
• Attack Vector: Network (AV:N). Exploitation occurs via specifically crafted HTTP requests.
• Authentication: Not required (PR:N).
• User Interaction: Not required (UI:N).
• Affected Products and Versions:
  • Fortinet FortiSandbox versions 4.2.0 through 4.2.8
  • Fortinet FortiSandbox versions 4.4.0 through 4.4.8
  • Fortinet FortiSandbox versions 5.0.0 through 5.0.5
  • Fortinet FortiSandbox Cloud versions 5.0.4 through 5.0.5
  • Fortinet FortiSandbox PaaS versions 5.0.4 through 5.0.5
• CVSS 3.1 Score: 9.8 (CRITICAL) – CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Detection

• Monitor FortiSandbox web server logs for unusual HTTP request patterns, especially in URI paths or POST body parameters, that may indicate command injection attempts (e.g., &, |, ;, `, $(), &&, || followed by system commands).
• Look for unexpected process creation originating from the FortiSandbox application’s user or web server process. This could include sh, bash, cmd.exe, powershell.exe, python, perl, wget, curl, nc, ncat, tftp, or other uncommon binaries.
• Monitor network egress from FortiSandbox appliances for connections to suspicious external IP addresses or domains, indicative of command and control (C2) or data exfiltration.
• Hunt for new or modified files in web root directories or system binaries that could indicate webshell deployment or persistence mechanisms.

Sigma Detection Rules

FortiSandbox OS Command Injection – Suspicious Process Spawn (Linux)

title: FortiSandbox OS Command Injection - Suspicious Process Spawn (Linux)
id: 0c2d3e4f-5a6b-7c8d-9e0f-1a2b3c4d5e6f
status: experimental
description: Detects suspicious process creation originating from common web server processes, indicative of successful OS command injection on a Linux-based system like FortiSandbox.
logsource:
  product: linux
  service: auditd
detection:
  selection_parent:
    ParentImage|endswith:
      - '/usr/sbin/httpd'
      - '/usr/sbin/nginx'
      - '/usr/sbin/apache2'
      - '/usr/bin/uwsgi'
      - '/usr/bin/gunicorn'
      - '/usr/bin/php-fpm'
      - '/opt/fortinet/fortisandbox/bin/webserver' # Placeholder, actual path might vary
  selection_child:
    Image|endswith:
      - '/bin/sh'
      - '/bin/bash'
      - '/usr/bin/wget'
      - '/usr/bin/curl'
      - '/usr/bin/python'
      - '/usr/bin/perl'
      - '/usr/bin/nc'
      - '/usr/bin/ncat'
      - '/usr/bin/tftp'
      - '/usr/bin/socat'
  condition: selection_parent and selection_child
level: high

FortiSandbox Web Log – OS Command Injection Attempt

title: FortiSandbox Web Log - OS Command Injection Attempt
id: 1a2b3c4d-5e6f-7a8b-9c0d-e1f2a3b4c5d6
status: experimental
description: Detects common OS command injection patterns in web server access logs, targeting FortiSandbox appliances.
logsource:
  category: webserver
  service: fortisandbox_web_access # Custom service for FortiSandbox web logs
detection:
  selection:
    cs-uri-query|contains:
      - '&id='
      - '|id='
      - ';id='
      - '`id='
      - '$('
      - '`'
      - '&&'
      - '||'
      - 'uname'
      - 'whoami'
      - 'cat /etc/passwd'
      - 'ls -la'
      - 'wget '
      - 'curl '
      - 'nc -e '
      - 'bash -c '
  condition: selection
level: medium

Mitigations

1. Patch Immediately: Apply the latest security updates provided by Fortinet for FortiSandbox, FortiSandbox Cloud, and FortiSandbox PaaS. Refer to the vendor advisory FG-IR-26-141 for specific patch versions.
2. Network Segmentation: Isolate FortiSandbox appliances on a dedicated network segment with strict ingress/egress filtering to limit potential lateral movement in case of compromise.
3. Restrict Access: Limit administrative access to FortiSandbox interfaces to trusted IP addresses and enforce strong authentication mechanisms.
4. Monitor Logs: Ensure comprehensive logging is enabled for FortiSandbox appliances and integrate logs with a SIEM for real-time monitoring and alerting.

References

• https://fortiguard.fortinet.com/psirt/FG-IR-26-141
• https://nvd.nist.gov/vuln/detail/CVE-2026-25089
• https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-25089
• https://arcticwolf.com/resources/blog/inside-fortibleed-reverse-engineering-the-cyberstrike-harvester-behind-a-global-fortigate-credential-factory/
• https://kudelskisecurity.com/research/fortinet-fortibleed-global-compromise-active-exploitation-of-fortinet-vulnerabilities

Indicators of Compromise

MITRE ATT&CK

• T1190 — Exploit Public-Facing Application
• T1059.004 — Unix Shell
• T1133 — External Remote Services
• T1539 — Steal Web Session Cookie
• T1087.002 — Domain Account
• T1069.002 — Domain Groups
• T1119 — Automated Collection
• T1040 — Network Sniffing
• T1135 — Network Share Discovery
• T1558.004 — AS-REP Roasting
• T1552 — Unsecured Credentials
• T1021.002 — SMB/Windows Admin Shares
• T1602.002 — Network Device Configuration Dump
• T1110.003 — Password Spraying
• T1020 — Automated Exfiltration
• T1552.001 — Credentials In Files
• T1048.002 — Exfiltration Over Asymmetric Encrypted Non-C2 Protocol
• T1039 — Data from Network Shared Drive
• T1078 — Valid Accounts
• T1110.004 — Credential Stuffing
• T1018 — Remote System Discovery
• T1046 — Network Service Discovery
• T1558.003 — Kerberoasting
• T1110 — Brute Force
• T1110.002 — Password Cracking
• T1595 — Active Scanning