CVE-2024-51249
📋 TL;DR
This vulnerability allows remote attackers to execute arbitrary commands on Draytek Vigor3900 routers by injecting malicious commands into the mainfunction.cgi endpoint and calling the reboot function. This affects all organizations using the vulnerable firmware version of these routers, potentially giving attackers full control over network infrastructure.
💻 Affected Systems
- Draytek Vigor3900
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete compromise of the router allowing attackers to intercept all network traffic, pivot to internal systems, install persistent backdoors, or disable network connectivity entirely.
Likely Case
Attackers gain remote code execution to install malware, create backdoors, or use the router as a pivot point for further attacks on the internal network.
If Mitigated
Limited impact if network segmentation prevents lateral movement and regular monitoring detects anomalous reboot activity.
🎯 Exploit Status
The GitHub reference contains technical details that could be used to create working exploits. The vulnerability requires no authentication and has simple command injection.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Unknown
Vendor Advisory: Unknown
Restart Required: Yes
Instructions:
1. Check Draytek's official website for security advisories. 2. Download the latest firmware if available. 3. Backup current configuration. 4. Upload and install new firmware via web interface. 5. Restart the router.
🔧 Temporary Workarounds
Block CGI endpoint access
linuxUse firewall rules to block external access to mainfunction.cgi endpoint
iptables -A INPUT -p tcp --dport 80 -m string --string "mainfunction.cgi" --algo bm -j DROP
iptables -A INPUT -p tcp --dport 443 -m string --string "mainfunction.cgi" --algo bm -j DROP
Disable web management interface
allDisable remote web management if not required
🧯 If You Can't Patch
- Segment the router on a dedicated VLAN with strict firewall rules limiting inbound and outbound connections
- Implement network monitoring for unusual reboot patterns or CGI endpoint access attempts
🔍 How to Verify
Check if Vulnerable:
Check firmware version in router web interface under System Maintenance > Firmware InformationCheck Version:
curl -k https://[router-ip]/cgi-bin/mainfunction.cgi?action=reboot (DO NOT RUN ON PRODUCTION - test only)Verify Fix Applied:
Verify firmware version is no longer 1.5.1.3 and test if command injection via mainfunction.cgi is possible📡 Detection & Monitoring
Log Indicators:
- Unusual reboot events in system logs
- Access to mainfunction.cgi with suspicious parameters
- Multiple failed authentication attempts followed by CGI access
Network Indicators:
- HTTP requests to /cgi-bin/mainfunction.cgi with command injection patterns
- Unusual outbound connections from router to external IPs
- Sudden network disruption followed by router reboot
SIEM Query:
source="router_logs" AND ("mainfunction.cgi" OR "reboot") AND (cmd=* OR exec=* OR system=* OR | OR ; OR $)