CVE-2024-46568
📋 TL;DR
This vulnerability allows attackers to cause a Denial of Service (DoS) on Draytek Vigor 3910 routers by exploiting a buffer overflow in the sPeerId parameter of the vpn.cgi component. Attackers can crash the device or potentially execute arbitrary code by sending specially crafted input. Organizations using the affected router version are at risk.
💻 Affected Systems
- Draytek Vigor 3910
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete device crash requiring physical reboot, potential remote code execution leading to full device compromise, and VPN service disruption affecting all connected users.
Likely Case
Denial of Service causing VPN connectivity loss, device instability requiring reboot, and temporary network disruption for connected clients.
If Mitigated
Minimal impact with proper network segmentation, firewall rules blocking external access to management interfaces, and monitoring for abnormal traffic patterns.
🎯 Exploit Status
Buffer overflow vulnerabilities in web interfaces typically have low exploitation complexity, especially when unauthenticated.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Unknown
Vendor Advisory: Not available
Restart Required: Yes
Instructions:
1. Check Draytek website for security advisories
2. Download latest firmware if available
3. Backup current configuration
4. Upload and install new firmware
5. Reboot device
6. Restore configuration if needed
🔧 Temporary Workarounds
Restrict VPN CGI Access
linuxBlock external access to vpn.cgi interface using firewall rules
iptables -A INPUT -p tcp --dport 443 -m string --string "vpn.cgi" --algo bm -j DROP
Disable Unused VPN Features
allTurn off VPN services if not required for business operations
🧯 If You Can't Patch
- Implement strict network segmentation to isolate the router from untrusted networks
- Deploy intrusion detection/prevention systems to monitor for buffer overflow attempts
🔍 How to Verify
Check if Vulnerable:
Check router web interface or CLI for firmware version; if version is exactly v4.3.2.6, device is vulnerableCheck Version:
ssh admin@router-ip "show version" or check web interface System Status pageVerify Fix Applied:
Verify firmware version has changed from v4.3.2.6 to a newer version📡 Detection & Monitoring
Log Indicators:
- Multiple failed VPN connection attempts
- Device reboot events without admin action
- Large payloads sent to vpn.cgi endpoint
Network Indicators:
- Unusual traffic patterns to router's VPN port
- Large HTTP POST requests to /vpn.cgi
- Connection attempts with abnormally long sPeerId parameters
SIEM Query:
source="router_logs" AND (uri="*vpn.cgi*" AND content_length>1000) OR event_type="system_reboot"