CVE-2021-20731
📋 TL;DR
This vulnerability allows remote attackers to execute arbitrary operating system commands with root privileges on affected Buffalo WSR-1166DHP3 and WSR-1166DHP4 wireless routers. Attackers can gain complete control of the device through unspecified vectors. Organizations and individuals using these specific router models with vulnerable firmware versions are affected.
💻 Affected Systems
- Buffalo WSR-1166DHP3
- Buffalo WSR-1166DHP4
📦 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, or use the device for botnet activities.
Likely Case
Attackers gain root access to the router, enabling them to modify DNS settings, intercept credentials, or disable security features.
If Mitigated
If properly segmented and monitored, impact limited to the router itself with minimal lateral movement potential.
🎯 Exploit Status
The advisory mentions 'unspecified vectors' but confirms unauthenticated remote code execution with root privileges.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: WSR-1166DHP3 firmware Ver.1.17 or later, WSR-1166DHP4 firmware Ver.1.03 or later
Vendor Advisory: https://www.buffalo.jp/news/detail/20210531-01.html
Restart Required: Yes
Instructions:
1. Download latest firmware from Buffalo support site. 2. Log into router admin interface. 3. Navigate to firmware update section. 4. Upload and apply new firmware. 5. Wait for automatic reboot.
🔧 Temporary Workarounds
Network Segmentation
allIsolate affected routers in separate network segments to limit potential lateral movement.
Access Control Lists
allImplement strict firewall rules to limit access to router management interfaces.
🧯 If You Can't Patch
- Replace affected routers with patched or alternative models
- Implement network monitoring for suspicious router traffic and configuration changes
🔍 How to Verify
Check if Vulnerable:
Check router admin interface for firmware version. If WSR-1166DHP3 is ≤1.16 or WSR-1166DHP4 is ≤1.02, device is vulnerable.Check Version:
Login to router web interface and check System Information or Firmware Update pageVerify Fix Applied:
After update, confirm firmware version shows WSR-1166DHP3 ≥1.17 or WSR-1166DHP4 ≥1.03 in admin interface.📡 Detection & Monitoring
Log Indicators:
- Unexpected configuration changes
- Unusual process execution
- Failed authentication attempts to router
Network Indicators:
- Unusual outbound connections from router
- DNS hijacking patterns
- Traffic redirection
SIEM Query:
source="router_logs" AND (event_type="config_change" OR event_type="command_execution")