CVE-2020-15833
📋 TL;DR
This vulnerability allows remote attackers to gain root access to affected Mofi Network routers via SSH using a hard-coded public key stored in read-only memory. The key cannot be removed or modified by device owners, creating a permanent backdoor. All users of affected MOFI4500-4GXeLTE devices running version 4.1.5-std are impacted.
💻 Affected Systems
- Mofi Network MOFI4500-4GXeLTE
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete compromise of router with root access, allowing attackers to intercept all network traffic, modify configurations, install persistent malware, and pivot to internal networks.
Likely Case
Unauthorized root access leading to network monitoring, credential theft, and potential lateral movement to connected devices.
If Mitigated
Limited impact if SSH is disabled or firewalled, though the backdoor remains present in the firmware.
🎯 Exploit Status
Exploitation requires only SSH access to the device and knowledge of the hard-coded key. No authentication is needed beyond network access to SSH port.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 4.2.0 or later
Vendor Advisory: https://mofinetwork.com/index.php?main_page=page&id=14
Restart Required: Yes
Instructions:
1. Log into router admin interface. 2. Navigate to System > Firmware Upgrade. 3. Download latest firmware from Mofi Network website. 4. Upload and apply firmware update. 5. Reboot router after update completes.
🔧 Temporary Workarounds
Disable SSH Service
linuxCompletely disable SSH access to prevent exploitation of this vulnerability.
ssh root@router_ip 'service dropbear stop'
ssh root@router_ip 'chkconfig dropbear off'
Restrict SSH Access with Firewall
linuxConfigure firewall rules to only allow SSH from trusted IP addresses.
iptables -A INPUT -p tcp --dport 22 -s trusted_ip -j ACCEPT
iptables -A INPUT -p tcp --dport 22 -j DROP
🧯 If You Can't Patch
- Isolate affected routers in separate network segments with strict firewall rules.
- Implement network monitoring and intrusion detection specifically for SSH authentication attempts to the affected devices.
🔍 How to Verify
Check if Vulnerable:
Check if SSH accepts the hard-coded key by attempting SSH connection with known exploit methods or checking Dropbear configuration for alternate key paths.Check Version:
ssh root@router_ip 'cat /etc/version' or check admin web interface System Status pageVerify Fix Applied:
Verify firmware version is 4.2.0 or later and attempt SSH connection with hard-coded key should fail.📡 Detection & Monitoring
Log Indicators:
- Successful SSH root logins from unexpected sources
- SSH authentication attempts using unusual key paths
- Multiple failed SSH attempts followed by successful login
Network Indicators:
- SSH connections to router on port 22 from unauthorized IPs
- Unusual outbound traffic from router after SSH connection
SIEM Query:
source="router_logs" (event="ssh_login" AND user="root" AND result="success") OR (event="ssh_auth" AND key_path="/rom/*")