CVE-2021-20144
📋 TL;DR
An unauthenticated command injection vulnerability in Gryphon Tower routers allows attackers on the same network to execute arbitrary commands as root by sending malicious packets to port 9999. This affects all users of vulnerable Gryphon Tower router models, enabling complete device compromise without authentication.
💻 Affected Systems
- Gryphon Tower routers
📦 What is this software?
Gryphon Tower Firmware by Gryphonconnect
⚠️ Risk & Real-World Impact
Worst Case
Complete router takeover allowing traffic interception, malware deployment, network pivoting, and persistent backdoor installation.
Likely Case
Router compromise leading to DNS hijacking, credential theft from network traffic, and botnet recruitment.
If Mitigated
Limited impact if network segmentation isolates routers and strict firewall rules block port 9999 access.
🎯 Exploit Status
Exploit requires crafting specific packets to operation 49; public technical details available.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: GryphonOS 4.0.0 and later
Vendor Advisory: https://www.gryphonconnect.com/security-advisory/
Restart Required: Yes
Instructions:
1. Log into Gryphon admin interface. 2. Navigate to Settings > Firmware Update. 3. Check for and install GryphonOS 4.0.0 or later. 4. Reboot router after update completes.
🔧 Temporary Workarounds
Block controller_server port
linuxBlock access to port 9999 on the router using firewall rules.
iptables -A INPUT -p tcp --dport 9999 -j DROP
iptables -A INPUT -p udp --dport 9999 -j DROP
Disable controller_server service
linuxStop and disable the vulnerable controller_server service.
systemctl stop controller_server
systemctl disable controller_server
🧯 If You Can't Patch
- Segment router on isolated network VLAN to limit attack surface.
- Implement strict network access controls to prevent unauthorized devices from reaching router management interfaces.
🔍 How to Verify
Check if Vulnerable:
Check if controller_server is listening on port 9999: 'netstat -tulpn | grep :9999' or 'ss -tulpn | grep :9999'. If service is running on pre-4.0.0 firmware, device is vulnerable.Check Version:
Check admin interface or use 'cat /etc/gryphon-version' if shell access available.Verify Fix Applied:
Verify GryphonOS version is 4.0.0 or later in admin interface and confirm port 9999 is no longer listening or service is patched.📡 Detection & Monitoring
Log Indicators:
- Unusual connections to port 9999
- Suspicious command execution in system logs
- Unexpected process creation from controller_server
Network Indicators:
- Malformed packets to port 9999 with operation code 49
- Unusual outbound connections from router after exploitation
SIEM Query:
source_port:9999 AND (payload_contains:"operation=49" OR packet_size_abnormal)