CVE-2021-26747
📋 TL;DR
This vulnerability allows remote attackers to execute arbitrary commands on Netis WF2780 and WF2411 routers by injecting shell metacharacters into the ping command. Attackers can gain full control of affected devices without authentication. Organizations using these specific Netis router models are at risk.
💻 Affected Systems
- Netis WF2780
- Netis WF2411
📦 What is this software?
Wf2411 Firmware by Netis Systems
Wf2780 Firmware by Netis Systems
⚠️ Risk & Real-World Impact
Worst Case
Complete compromise of router leading to network interception, credential theft, lateral movement to internal systems, and persistent backdoor installation.
Likely Case
Router takeover enabling traffic monitoring, DNS hijacking, and use as attack platform against internal network.
If Mitigated
Limited impact if routers are isolated in separate VLANs with strict network segmentation and monitoring.
🎯 Exploit Status
Proof-of-concept code available on GitHub; exploitation requires network access to router management interface.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Unknown
Vendor Advisory: http://www.netis-systems.com.tw/
Restart Required: No
Instructions:
Check vendor website for firmware updates. If no patch available, consider replacing affected devices with supported models.
🔧 Temporary Workarounds
Disable WAN Management
allPrevent external access to router management interface
Access router admin panel → Security → Remote Management → Disable
Network Segmentation
allIsolate routers in separate VLAN with restricted access
🧯 If You Can't Patch
- Replace affected routers with supported models from different vendors
- Implement strict firewall rules blocking all external access to router management interfaces
🔍 How to Verify
Check if Vulnerable:
Check router firmware version in admin panel: System Status → Firmware VersionCheck Version:
Login to router web interface and navigate to firmware information pageVerify Fix Applied:
Verify firmware version is updated beyond vulnerable versions or test with known exploit payloads📡 Detection & Monitoring
Log Indicators:
- Unusual ping commands with special characters in router logs
- Multiple failed authentication attempts followed by ping requests
Network Indicators:
- HTTP requests to router management interface with shell metacharacters in parameters
- Outbound connections from router to unexpected destinations
SIEM Query:
source="router_logs" AND (message="ping" AND (message="$" OR message="|" OR message="&"))