CVE-2024-51253
📋 TL;DR
This vulnerability allows remote attackers to execute arbitrary commands on Draytek Vigor3900 routers by injecting malicious commands into the mainfunction.cgi component. Attackers can exploit this by calling the doL2TP function, leading to command injection. Organizations using affected Draytek Vigor3900 routers are at risk.
💻 Affected Systems
- Draytek Vigor3900
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete system compromise allowing attackers to install backdoors, steal credentials, pivot to internal networks, or deploy ransomware.
Likely Case
Unauthorized access to router configuration, network reconnaissance, credential harvesting, and potential lateral movement to connected systems.
If Mitigated
Limited impact with proper network segmentation, but still potential for router compromise and denial of service.
🎯 Exploit Status
The GitHub reference contains technical details that could facilitate exploitation. Command injection vulnerabilities are typically easy to weaponize.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Unknown
Vendor Advisory: Unknown
Restart Required: No
Instructions:
Check Draytek's official website for security updates. If a patch is available, download the firmware update file, log into the router's web interface, navigate to System Maintenance > Firmware Upgrade, upload the file, and apply the update.
🔧 Temporary Workarounds
Disable Web Management Interface
allDisable the web-based management interface to prevent exploitation.
Log into router CLI or web interface
Navigate to System Maintenance > Management
Disable HTTP/HTTPS management or restrict to specific IPs
Restrict Management Access
allLimit management interface access to specific trusted IP addresses only.
Log into router web interface
Navigate to System Maintenance > Management
Configure IP address restrictions for management access
🧯 If You Can't Patch
- Implement strict network segmentation to isolate the router from critical systems
- Deploy a web application firewall (WAF) with command injection protection rules
🔍 How to Verify
Check if Vulnerable:
Check the firmware version in the router's web interface under System Maintenance > Firmware Information. If version is 1.5.1.3, the system is vulnerable.Check Version:
Log into router web interface and navigate to System Maintenance > Firmware InformationVerify Fix Applied:
After applying any update, verify the firmware version is no longer 1.5.1.3. Test the doL2TP function with safe commands to ensure command injection is prevented.📡 Detection & Monitoring
Log Indicators:
- Unusual command execution in system logs
- Multiple failed authentication attempts followed by successful access
- Suspicious CGI requests to mainfunction.cgi with command parameters
Network Indicators:
- Unusual outbound connections from the router
- Traffic patterns indicating command and control activity
- Unexpected port scans originating from the router
SIEM Query:
source="router_logs" AND ("mainfunction.cgi" OR "doL2TP") AND (cmd.exe OR /bin/sh OR bash OR powershell)