CVE-2021-20160
📋 TL;DR
This CVE describes a command injection vulnerability in Trendnet AC2600 routers that allows attackers to execute arbitrary commands as root by injecting malicious input into the SMB username parameter. The vulnerability affects users of Trendnet AC2600 TEW-827DRU routers with vulnerable firmware versions. Successful exploitation gives attackers complete control over the affected device.
💻 Affected Systems
- Trendnet AC2600 TEW-827DRU
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete device compromise allowing attackers to install persistent backdoors, intercept network traffic, pivot to internal networks, or use the device as part of a botnet.
Likely Case
Attackers gain root access to the router, enabling them to modify network settings, intercept traffic, or use the device for further attacks.
If Mitigated
With proper network segmentation and access controls, impact is limited to the affected device only.
🎯 Exploit Status
Exploitation requires authentication to the web interface. The vulnerability is well-documented with public proof-of-concept code available.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 2.08B02 or later
Vendor Advisory: https://www.trendnet.com/support/
Restart Required: Yes
Instructions:
1. Log into Trendnet router web interface. 2. Navigate to Administration > Firmware Upgrade. 3. Download latest firmware from Trendnet website. 4. Upload and install firmware. 5. Reboot router after installation.
🔧 Temporary Workarounds
Disable SMB functionality
allDisable SMB file sharing on the router to remove the vulnerable component
Navigate to USB Storage > File Sharing and disable SMB
Restrict web interface access
allLimit access to the router's web administration interface
Navigate to Advanced > Firewall and restrict admin access to trusted IPs only
🧯 If You Can't Patch
- Segment affected routers on isolated network segments
- Implement strict firewall rules to limit router management interface access
🔍 How to Verify
Check if Vulnerable:
Check firmware version in router web interface under Administration > StatusCheck Version:
Check via web interface or SSH if enabled: cat /etc/versionVerify Fix Applied:
Verify firmware version is 2.08B02 or later after patching📡 Detection & Monitoring
Log Indicators:
- Unusual SMB configuration changes
- Multiple failed login attempts to web interface
- Unexpected command execution in system logs
Network Indicators:
- Unusual outbound connections from router
- SMB traffic to unexpected destinations
- Router making DNS queries to suspicious domains
SIEM Query:
source="router_logs" AND ("SMB" OR "username" OR "command injection")