CVE-2021-43073
📋 TL;DR
This OS command injection vulnerability in Fortinet FortiWeb allows attackers to execute arbitrary commands on affected devices via specially crafted HTTP requests. It affects FortiWeb versions 6.4.1 and below, 6.3.15 and below, and 6.2.6 and below. Successful exploitation could lead to complete system compromise.
💻 Affected Systems
- Fortinet FortiWeb
📦 What is this software?
Fortiweb by Fortinet
Fortiweb by Fortinet
Fortiweb by Fortinet
⚠️ Risk & Real-World Impact
Worst Case
Full system compromise allowing attacker to execute arbitrary commands with web server privileges, potentially leading to data theft, lateral movement, or installation of persistent backdoors.
Likely Case
Unauthorized command execution allowing attackers to read sensitive files, modify configurations, or disrupt services on the FortiWeb device.
If Mitigated
Limited impact with proper network segmentation and access controls preventing external exploitation attempts.
🎯 Exploit Status
The vulnerability allows unauthenticated exploitation via crafted HTTP requests, making it relatively easy to weaponize. No public proof-of-concept has been released as of knowledge cutoff.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: FortiWeb 6.4.2, 6.3.16, 6.2.7
Vendor Advisory: https://fortiguard.com/advisory/FG-IR-21-180
Restart Required: Yes
Instructions:
1. Download the patched firmware version from Fortinet support portal. 2. Backup current configuration. 3. Upload and install the new firmware via FortiWeb web interface or CLI. 4. Reboot the device. 5. Verify the update was successful.
🔧 Temporary Workarounds
Restrict Management Interface Access
allLimit access to FortiWeb management interface to trusted IP addresses only
Configure firewall rules to restrict access to FortiWeb management IP/ports
Network Segmentation
allPlace FortiWeb devices in isolated network segments with strict inbound/outbound controls
Implement VLAN segmentation and firewall rules to isolate FortiWeb management traffic
🧯 If You Can't Patch
- Implement strict network access controls to limit HTTP access to FortiWeb management interfaces
- Deploy web application firewall rules to block suspicious HTTP request patterns
🔍 How to Verify
Check if Vulnerable:
Check FortiWeb firmware version via web interface (System > Status) or CLI command 'get system status'Check Version:
get system status | grep VersionVerify Fix Applied:
Verify firmware version is 6.4.2 or higher, 6.3.16 or higher, or 6.2.7 or higher📡 Detection & Monitoring
Log Indicators:
- Unusual HTTP requests to FortiWeb management interface
- Suspicious command execution in system logs
- Failed authentication attempts followed by successful command execution
Network Indicators:
- HTTP requests with command injection patterns to FortiWeb management ports
- Unusual outbound connections from FortiWeb device
SIEM Query:
source="fortiweb" AND (http_request CONTAINS "|" OR http_request CONTAINS ";" OR http_request CONTAINS "`" OR http_request CONTAINS "$(")