CVE-2021-20709
📋 TL;DR
This vulnerability allows attackers with administrative privileges to execute arbitrary operating system commands on affected NEC Aterm routers by sending specially crafted requests to a specific URL. It affects NEC Aterm WF1200CR, WG1200CR, and WG2600HS routers running vulnerable firmware versions. Attackers can gain full control of the router and potentially pivot to internal networks.
💻 Affected Systems
- NEC Aterm WF1200CR
- NEC Aterm WG1200CR
- NEC Aterm WG2600HS
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete router compromise leading to persistent backdoor installation, credential theft, network traffic interception, and lateral movement to internal systems.
Likely Case
Router takeover enabling network reconnaissance, DNS hijacking, traffic redirection, and potential credential harvesting from connected devices.
If Mitigated
Limited impact if administrative access is restricted and network segmentation prevents lateral movement from compromised routers.
🎯 Exploit Status
Exploitation requires administrative credentials but is straightforward once obtained. No public exploit code is available.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: WF1200CR: >Ver1.3.2, WG1200CR: >Ver1.3.3, WG2600HS: >Ver1.5.1
Vendor Advisory: https://jpn.nec.com/security-info/secinfo/nv21-010.html
Restart Required: Yes
Instructions:
1. Log into router admin interface. 2. Navigate to firmware update section. 3. Download latest firmware from NEC support site. 4. Upload and apply firmware update. 5. Reboot router after update completes.
🔧 Temporary Workarounds
Restrict administrative access
allLimit administrative interface access to trusted IP addresses only
Configure firewall rules to restrict access to router admin interface (typically port 80/443) to specific management IPs
Change default credentials
allUse strong, unique administrative passwords
Change admin password via router web interface: System > Administration > Password
🧯 If You Can't Patch
- Isolate affected routers in separate VLAN with strict firewall rules
- Implement network monitoring for unusual administrative access patterns
🔍 How to Verify
Check if Vulnerable:
Check firmware version in router web interface: System > Firmware InformationCheck Version:
Check via web interface or SSH if enabled: show version or cat /proc/versionVerify Fix Applied:
Verify firmware version is above vulnerable versions: WF1200CR >1.3.2, WG1200CR >1.3.3, WG2600HS >1.5.1📡 Detection & Monitoring
Log Indicators:
- Unusual administrative login patterns
- Multiple failed login attempts followed by successful login
- Unexpected configuration changes
Network Indicators:
- Unusual outbound connections from router
- DNS queries to suspicious domains
- Traffic redirection patterns
SIEM Query:
source="router_logs" AND (event="admin_login" AND user="admin") OR (url="*specific_vulnerable_endpoint*")