CVE-2024-51300
📋 TL;DR
This vulnerability allows remote attackers to execute arbitrary commands on Draytek Vigor3900 routers by injecting malicious commands into the mainfunction.cgi endpoint. Attackers can achieve remote code execution with high privileges, affecting all organizations using the vulnerable firmware version.
💻 Affected Systems
- Draytek Vigor3900
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete system compromise allowing attackers to install persistent backdoors, steal credentials, pivot to internal networks, or render the router inoperable.
Likely Case
Attackers gain shell access to execute commands, potentially stealing network configuration, intercepting traffic, or using the router as a foothold for further attacks.
If Mitigated
With proper network segmentation and access controls, impact is limited to the router itself, though it could still serve as an entry point.
🎯 Exploit Status
The exploit requires sending crafted HTTP requests to the vulnerable endpoint. Public proof-of-concept details are available in the GitHub reference.
🛠️ 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
linuxRestrict access to the vulnerable mainfunction.cgi endpoint using firewall rules or web application firewall.
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
🧯 If You Can't Patch
- Isolate the router in a dedicated network segment with strict firewall rules limiting inbound and outbound connections.
- Implement network monitoring to detect exploitation attempts and anomalous traffic patterns from the router.
🔍 How to Verify
Check if Vulnerable:
Check firmware version via web interface: Login > System Maintenance > Firmware Information. If version is 1.5.1.3, the device is vulnerable.Check Version:
curl -k https://[router-ip]/cgi-bin/mainfunction.cgi?action=get_rrd&test=$(id)Verify Fix Applied:
After updating firmware, verify the version is no longer 1.5.1.3 and test that mainfunction.cgi endpoint no longer accepts command injection.📡 Detection & Monitoring
Log Indicators:
- Unusual CGI requests to mainfunction.cgi with command injection patterns
- System logs showing unexpected command execution
- Failed authentication attempts followed by CGI access
Network Indicators:
- HTTP requests containing shell metacharacters like ;, |, &, $() in URL parameters
- Outbound connections from router to unexpected external IPs
SIEM Query:
source="router_logs" AND (url="*mainfunction.cgi*" AND (url="*;*" OR url="*|*" OR url="*$(*" OR url="*`*"))