CVE-2021-20711
📋 TL;DR
This vulnerability allows remote attackers to execute arbitrary operating system commands on affected Aterm WG2600HS routers. Attackers can potentially take full control of the device without authentication. All users running firmware version 1.5.1 or earlier are affected.
💻 Affected Systems
- Aterm WG2600HS
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete compromise of the router allowing attackers to intercept all network traffic, install persistent backdoors, pivot to internal networks, and use the device for botnet activities.
Likely Case
Router takeover leading to DNS hijacking, credential theft from network traffic, and use as a foothold for attacking other devices on the network.
If Mitigated
Limited impact if device is behind strict firewall rules and not internet-facing, though internal attackers could still exploit.
🎯 Exploit Status
The vulnerability allows OS command injection via unspecified vectors, suggesting relatively straightforward exploitation once details are known.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Firmware version newer than 1.5.1
Vendor Advisory: https://jpn.nec.com/security-info/secinfo/nv21-010.html
Restart Required: Yes
Instructions:
1. Download latest firmware from NEC official site. 2. Log into router admin interface. 3. Navigate to firmware update section. 4. Upload and apply new firmware. 5. Router will automatically restart.
🔧 Temporary Workarounds
Network Segmentation
allIsolate router from critical internal networks and restrict access
Access Control
allImplement strict firewall rules to limit who can access router management interface
🧯 If You Can't Patch
- Replace the router with a different model that receives security updates
- Deploy the router in a DMZ with no access to internal networks
🔍 How to Verify
Check if Vulnerable:
Check firmware version in router web interface under System Information or similar sectionCheck Version:
Login to router web interface and navigate to System Status or Firmware Information pageVerify Fix Applied:
Verify firmware version is newer than 1.5.1 after update📡 Detection & Monitoring
Log Indicators:
- Unusual command execution in system logs
- Multiple failed login attempts followed by successful access
- Unexpected firmware or configuration changes
Network Indicators:
- Unusual outbound connections from router
- DNS queries to suspicious domains
- Unexpected port scans originating from router
SIEM Query:
source="router_logs" AND (command="*;*" OR command="*|*" OR command="*`*" OR command="*$(*")