CVE-2025-52364
📋 TL;DR
The Tenda CP3 Pro router firmware has an insecure permissions vulnerability that enables the telnet service by default at boot, allowing remote attackers to connect to the device's shell over the network. This could lead to unauthorized access if default or weak credentials are present. All users running the affected firmware version are impacted.
💻 Affected Systems
- Tenda CP3 Pro
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Full device compromise leading to network infiltration, data exfiltration, malware deployment, and use as a botnet node.
Likely Case
Unauthorized access to device shell, configuration changes, credential harvesting, and lateral movement within the network.
If Mitigated
Limited to attempted connection logs if strong authentication and network controls are implemented.
🎯 Exploit Status
Simple telnet connection attempt with default/weak credentials; detailed in public references.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Unknown
Vendor Advisory: https://www.tendacn.com/product/download/cp3pro.html
Restart Required: Yes
Instructions:
1. Check vendor website for updated firmware. 2. Download and verify firmware. 3. Upload via admin interface. 4. Apply update and restart device.
🔧 Temporary Workarounds
Disable Telnet Service
linuxPrevent telnetd from starting at boot by modifying or disabling the initialization script.
chmod -x /etc/init.d/eth.sh
rm /etc/init.d/eth.sh
killall telnetd
Network Access Control
linuxBlock telnet port (23) at firewall to prevent remote connections.
iptables -A INPUT -p tcp --dport 23 -j DROP
🧯 If You Can't Patch
- Implement strict network segmentation to isolate affected devices.
- Enable strong authentication and change all default credentials immediately.
🔍 How to Verify
Check if Vulnerable:
Check if telnet service is running: 'ps aux | grep telnetd' or 'netstat -tlnp | grep :23'Check Version:
Check firmware version in web interface or via CLI: 'cat /etc/version'Verify Fix Applied:
Verify telnet service is not running and port 23 is closed: 'netstat -tlnp | grep :23' should return empty.📡 Detection & Monitoring
Log Indicators:
- Failed/successful telnet authentication attempts in system logs
- Unexpected telnetd process execution
Network Indicators:
- Telnet connections (TCP port 23) to router IP
- Brute-force attempts on telnet service
SIEM Query:
source="router_logs" AND (process="telnetd" OR port=23)