CVE-2024-35396
📋 TL;DR
This vulnerability involves a hardcoded root password in the TOTOLINK CP900L router's configuration file, allowing attackers to gain administrative access via telnet. Anyone using the affected firmware version is vulnerable to complete device compromise. Attackers can execute arbitrary commands, modify configurations, or use the device as a foothold for further attacks.
💻 Affected Systems
- TOTOLINK CP900L
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete device takeover leading to network compromise, data exfiltration, malware deployment, or use as a botnet node.
Likely Case
Unauthorized administrative access allowing configuration changes, service disruption, or credential harvesting.
If Mitigated
Limited impact if telnet is disabled and strong perimeter controls prevent external access.
🎯 Exploit Status
Exploitation requires telnet access; attackers need network reachability to the device's telnet port.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Unknown
Vendor Advisory: http://totolink.com
Restart Required: No
Instructions:
Check vendor website for firmware updates; if available, download and install via web interface.
🔧 Temporary Workarounds
Disable Telnet Service
linuxPrevent telnet access to eliminate the attack vector.
telnetd -l /bin/sh -p 23
Block Telnet Port
linuxUse firewall rules to block external telnet access.
iptables -A INPUT -p tcp --dport 23 -j DROP
🧯 If You Can't Patch
- Isolate the device on a separate VLAN with strict access controls.
- Implement network monitoring for telnet authentication attempts and unusual root logins.
🔍 How to Verify
Check if Vulnerable:
Check if telnet is accessible on port 23 and test login with known hardcoded credentials.Check Version:
Check firmware version in web interface or via CLI: cat /proc/versionVerify Fix Applied:
Verify telnet service is disabled or inaccessible, and test login fails with hardcoded credentials.📡 Detection & Monitoring
Log Indicators:
- Failed/successful telnet authentication attempts
- Root login via telnet
Network Indicators:
- Telnet traffic to device on port 23
- Unusual outbound connections from device
SIEM Query:
source="router_logs" AND (event="telnet_login" OR user="root")