CVE-2024-39800
📋 TL;DR
This vulnerability allows authenticated attackers to execute arbitrary commands on Wavlink AC3000 routers by exploiting configuration injection in the openvpn.cgi interface. Attackers can gain full system control through specially crafted HTTP requests. Only users of specific Wavlink router models with vulnerable firmware are affected.
💻 Affected Systems
- Wavlink AC3000 M33A8
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete system compromise allowing attackers to install persistent backdoors, pivot to internal networks, steal credentials, and use the device for further attacks.
Likely Case
Attackers gain shell access to the router, enabling network reconnaissance, traffic interception, and launching attacks against internal devices.
If Mitigated
Limited impact if proper network segmentation, authentication controls, and monitoring are in place to detect and block exploitation attempts.
🎯 Exploit Status
Exploitation requires authenticated access but is straightforward once credentials are obtained. The vulnerability is in a CGI script that processes user input without proper sanitization.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Unknown
Vendor Advisory: Not available
Restart Required: No
Instructions:
1. Check Wavlink website for firmware updates
2. Download latest firmware for AC3000 M33A8
3. Log into router admin interface
4. Navigate to firmware update section
5. Upload and apply new firmware
6. Verify version after update
🔧 Temporary Workarounds
Disable OpenVPN CGI endpoint
linuxRemove or restrict access to the vulnerable openvpn.cgi script
mv /www/cgi-bin/openvpn.cgi /www/cgi-bin/openvpn.cgi.disabled
chmod 000 /www/cgi-bin/openvpn.cgi.disabled
Restrict web interface access
linuxLimit admin interface access to trusted IP addresses only
iptables -A INPUT -p tcp --dport 80 -s TRUSTED_IP -j ACCEPT
iptables -A INPUT -p tcp --dport 443 -s TRUSTED_IP -j ACCEPT
iptables -A INPUT -p tcp --dport 80 -j DROP
iptables -A INPUT -p tcp --dport 443 -j DROP
🧯 If You Can't Patch
- Isolate affected routers in separate VLAN with strict firewall rules
- Implement network monitoring for suspicious HTTP requests to openvpn.cgi
🔍 How to Verify
Check if Vulnerable:
Check firmware version in router admin interface under System Status or About pageCheck Version:
curl -s http://router-ip/cgi-bin/luci/admin/status/overview | grep -i versionVerify Fix Applied:
Verify firmware version is newer than V5030.210505 and test if openvpn.cgi endpoint still accepts malicious input📡 Detection & Monitoring
Log Indicators:
- HTTP POST requests to /cgi-bin/openvpn.cgi with suspicious open_port parameters
- Unusual command execution in system logs
- Failed authentication attempts followed by successful login
Network Indicators:
- HTTP traffic to router admin interface from unexpected sources
- Outbound connections from router to suspicious IPs
SIEM Query:
source="router-logs" AND (url="/cgi-bin/openvpn.cgi" AND method="POST" AND (param="open_port" AND value CONTAINS "|" OR value CONTAINS ";" OR value CONTAINS "`"))