CVE-2024-41588
📋 TL;DR
This vulnerability allows authenticated users to exploit buffer overflows in DrayTek Vigor3910 devices by sending specially crafted POST requests to vulnerable CGI endpoints. Attackers could potentially execute arbitrary code, compromise the device, or cause denial of service. Only users with authentication credentials to affected DrayTek Vigor3910 devices are at risk.
💻 Affected Systems
- DrayTek Vigor3910
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Remote code execution leading to full device compromise, lateral movement into connected networks, and persistent backdoor installation.
Likely Case
Device crash/reboot causing denial of service, or limited code execution within device constraints.
If Mitigated
No impact if proper authentication controls prevent unauthorized access to vulnerable endpoints.
🎯 Exploit Status
Exploitation requires authentication and knowledge of buffer overflow techniques
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Versions after 4.3.2.6
Vendor Advisory: https://www.draytek.com/support/security-advisory/
Restart Required: Yes
Instructions:
1. Log into DrayTek Vigor3910 web interface
2. Navigate to System Maintenance > Firmware Upgrade
3. Download latest firmware from DrayTek support portal
4. Upload and apply firmware update
5. Reboot device after update completes
🔧 Temporary Workarounds
Disable CGI endpoints
linuxBlock access to vulnerable CGI endpoints if not required
iptables -A INPUT -p tcp --dport 80 -m string --string "v2x00.cgi" --algo bm -j DROP
iptables -A INPUT -p tcp --dport 80 -m string --string "cgiwcg.cgi" --algo bm -j DROP
Restrict access to management interface
allLimit management interface access to trusted IP addresses only
Configure firewall rules to restrict access to device management IP/ports
🧯 If You Can't Patch
- Implement strict access controls to limit authenticated users who can access device management
- Monitor logs for unusual POST requests to v2x00.cgi and cgiwcg.cgi endpoints
🔍 How to Verify
Check if Vulnerable:
Check firmware version via web interface: System Maintenance > Firmware InformationCheck Version:
curl -k https://[device-ip]/cgi-bin/mainfunction.cgi?action=versionVerify Fix Applied:
Verify firmware version is greater than 4.3.2.6📡 Detection & Monitoring
Log Indicators:
- Multiple POST requests to v2x00.cgi or cgiwcg.cgi with large parameter values
- Device crash/reboot logs following POST requests
Network Indicators:
- Unusual POST request patterns to CGI endpoints from authenticated users
- Large payloads sent to vulnerable endpoints
SIEM Query:
source="draytek" AND (uri="*v2x00.cgi*" OR uri="*cgiwcg.cgi*") AND method="POST" AND size_bytes>1024