CVE-2021-20149
📋 TL;DR
This vulnerability allows attackers to bypass IPv4 firewall rules and access all services on Trendnet AC2600 routers via IPv6 WAN interface. It affects Trendnet AC2600 TEW-827DRU routers with insufficient IPv6 access controls, exposing services like web administration, SSH, or other management interfaces to unauthorized external access.
💻 Affected Systems
- Trendnet AC2600 TEW-827DRU
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete device compromise via exposed administrative interfaces, credential theft, network infiltration, and potential pivot to internal network resources.
Likely Case
Unauthorized access to router management interface leading to configuration changes, credential harvesting, or service disruption.
If Mitigated
Limited exposure if IPv6 is disabled or proper IPv6 firewall rules are implemented.
🎯 Exploit Status
Exploitation requires IPv6 connectivity to target and knowledge of exposed services.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Check Trendnet for latest firmware updates
Vendor Advisory: https://www.trendnet.com/support/
Restart Required: Yes
Instructions:
1. Log into router admin interface
2. Navigate to firmware update section
3. Download latest firmware from Trendnet website
4. Upload and apply firmware update
5. Reboot router
🔧 Temporary Workarounds
Disable IPv6
allCompletely disable IPv6 functionality on the router
Login to router admin interface and disable IPv6 in network settings
Implement IPv6 firewall rules
linuxAdd iptables rules for IPv6 to mirror IPv4 restrictions
ip6tables -A INPUT -i wan -j DROP
ip6tables -A FORWARD -i wan -j DROP
🧯 If You Can't Patch
- Disable IPv6 on the router completely
- Place router behind external firewall with proper IPv6 filtering
- Change default credentials and restrict administrative access
🔍 How to Verify
Check if Vulnerable:
Check if IPv6 services are accessible from external network via nmap or similar tools: nmap -6 <router_ipv6_address>Check Version:
Check router admin interface for firmware version or use: ssh admin@router 'cat /etc/version'Verify Fix Applied:
Verify IPv6 services are no longer accessible externally and check firmware version is updated📡 Detection & Monitoring
Log Indicators:
- Unauthorized IPv6 connection attempts to router services
- Failed authentication attempts from IPv6 addresses
- Configuration changes from unexpected sources
Network Indicators:
- Unexpected IPv6 traffic to router management ports
- External IPv6 connections to internal services
SIEM Query:
source_ip=IPv6 AND dest_port IN (22,23,80,443,8080) AND device_type="router"