CVE-2021-43071
📋 TL;DR
This vulnerability allows remote attackers to execute arbitrary code on Fortinet FortiWeb web application firewalls via specially crafted HTTP requests to the LogReport API controller. Attackers can exploit a heap-based buffer overflow to gain unauthorized command execution. Organizations running affected FortiWeb versions are at risk.
💻 Affected Systems
- Fortinet FortiWeb
📦 What is this software?
Fortiweb by Fortinet
Fortiweb by Fortinet
Fortiweb by Fortinet
Fortiweb by Fortinet
⚠️ Risk & Real-World Impact
Worst Case
Full system compromise allowing attackers to execute arbitrary commands, install malware, pivot to internal networks, and potentially maintain persistent access.
Likely Case
Remote code execution leading to data exfiltration, service disruption, or deployment of ransomware on the FortiWeb device.
If Mitigated
Limited impact if proper network segmentation, API access controls, and monitoring are in place to detect and block exploitation attempts.
🎯 Exploit Status
Exploitation requires crafting specific HTTP requests to the vulnerable API endpoint.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: FortiWeb 6.4.2, 6.3.16, 6.2.7
Vendor Advisory: https://fortiguard.com/advisory/FG-IR-21-188
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 web interface or CLI. 4. Reboot the device after installation.
🔧 Temporary Workarounds
Restrict LogReport API Access
allLimit network access to the LogReport API controller using firewall rules or access control lists.
config system interface
edit <interface_name>
set allowaccess https ssh ping
end
Disable Unused API Endpoints
allIf LogReport API functionality is not required, disable it through configuration.
config system global
set admin-sport 443
set admin-https-redirect enable
end
🧯 If You Can't Patch
- Implement strict network segmentation to isolate FortiWeb devices from critical assets
- Deploy web application firewall rules to block suspicious HTTP requests to LogReport API endpoints
🔍 How to Verify
Check if Vulnerable:
Check FortiWeb firmware version via web interface (System > Dashboard) or CLI command: get system statusCheck 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 /api/v2.0/log/report endpoints
- Multiple failed authentication attempts followed by successful API access
- System logs showing unexpected process execution or configuration changes
Network Indicators:
- HTTP POST requests with abnormal payload sizes to LogReport API
- Traffic patterns indicating buffer overflow exploitation attempts
SIEM Query:
source="fortiweb" AND (uri_path="/api/v2.0/log/report" OR http_method="POST") AND (bytes_out>10000 OR status_code=500)