CVE-2020-28998
📋 TL;DR
This vulnerability allows remote attackers to gain full administrative control of Geeni GNC-CW013 smart doorbell devices via Telnet using a default static password. Attackers can execute arbitrary commands, modify device functionality, or use the device as a foothold into the network. Only Geeni GNC-CW013 doorbell version 1.8.1 is affected.
💻 Affected Systems
- Geeni GNC-CW013 Smart Video Doorbell
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete device compromise leading to unauthorized video/audio access, device bricking, lateral movement into internal networks, or participation in botnets.
Likely Case
Remote attackers gain root access to modify device settings, disable security features, or install malware for persistent access.
If Mitigated
With proper network segmentation and Telnet disabled, impact is limited to isolated device compromise without network access.
🎯 Exploit Status
Exploitation requires Telnet access and knowledge of the static password. Public proof-of-concept demonstrates the vulnerability.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Unknown
Vendor Advisory: https://support.mygeeni.com/hc/en-us
Restart Required: No
Instructions:
No official patch available. Contact Geeni support for firmware updates or replacement options.
🔧 Temporary Workarounds
Disable Telnet Service
linuxBlock or disable Telnet service on the device to prevent remote access.
iptables -A INPUT -p tcp --dport 23 -j DROP
systemctl stop telnet
chmod -x /usr/sbin/telnetd
Change Default Password
linuxIf Telnet must remain enabled, change the default password for all system accounts.
passwd root
passwd admin
🧯 If You Can't Patch
- Segment device on isolated VLAN with no access to critical network resources
- Implement network firewall rules to block Telnet (port 23) traffic to/from the device
🔍 How to Verify
Check if Vulnerable:
Attempt Telnet connection to device port 23 and test default credentials. Use nmap scan: nmap -p 23 --script telnet-brute <device_ip>Check Version:
Check device firmware version in Geeni mobile app settings or via device web interface if available.Verify Fix Applied:
Verify Telnet service is not accessible: telnet <device_ip> 23 should timeout or be refused. Test with known credentials should fail.📡 Detection & Monitoring
Log Indicators:
- Failed/successful Telnet authentication attempts
- Multiple connection attempts to port 23
- Unusual process execution from Telnet sessions
Network Indicators:
- Telnet traffic to/from doorbell device
- Unexpected outbound connections from device after Telnet access
SIEM Query:
source="doorbell" AND (port=23 OR protocol="telnet") AND (event_type="authentication" OR event_type="connection")