CVE-2018-21137
📋 TL;DR
NETGEAR D3600 and D6000 modem-routers contain a hardcoded administrative password that cannot be changed by users. This allows attackers with network access to gain full administrative control of affected devices. Devices running firmware versions before 1.0.0.76 are vulnerable.
💻 Affected Systems
- NETGEAR D3600
- NETGEAR D6000
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete device takeover allowing attackers to intercept all network traffic, install malware, pivot to internal networks, and permanently compromise the device.
Likely Case
Unauthorized administrative access leading to network traffic monitoring, DNS hijacking, credential theft, and device configuration changes.
If Mitigated
Limited impact if device is behind additional firewalls, not internet-facing, and network segmentation prevents lateral movement.
🎯 Exploit Status
Exploitation requires only network access and knowledge of the hardcoded credentials. No authentication or special conditions needed.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 1.0.0.76 or later
Vendor Advisory: https://kb.netgear.com/000060223/Security-Advisory-for-Hardcoded-Password-on-Some-Modem-Routers-PSV-2018-0099
Restart Required: Yes
Instructions:
1. Log into router admin interface. 2. Navigate to Advanced > Administration > Router Update. 3. Check for updates and install firmware version 1.0.0.76 or later. 4. Reboot device after update completes.
🔧 Temporary Workarounds
Network Segmentation
allPlace affected devices in isolated network segments to limit attack surface
Firewall Rules
allBlock external access to router administration interface
🧯 If You Can't Patch
- Replace affected devices with non-vulnerable models
- Implement strict network monitoring and anomaly detection for router traffic
🔍 How to Verify
Check if Vulnerable:
Check firmware version in router admin interface under Advanced > Administration > Router StatusCheck Version:
No CLI command available - must use web interfaceVerify Fix Applied:
Confirm firmware version is 1.0.0.76 or later in router admin interface📡 Detection & Monitoring
Log Indicators:
- Multiple failed login attempts followed by successful login
- Administrative configuration changes from unexpected IP addresses
Network Indicators:
- Unauthorized access to router administration ports (typically 80/443)
- Unusual outbound traffic from router
SIEM Query:
source_ip=ROUTER_IP AND (event_type="login_success" OR event_type="config_change")