CVE-2021-35326
📋 TL;DR
This vulnerability allows attackers to download the router's configuration file by sending a specially crafted HTTP request to the TOTOLINK A720R router. This affects users running firmware version v4.1.5cu.470_B20200911, potentially exposing sensitive network configuration and credentials.
💻 Affected Systems
- TOTOLINK A720R router
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Attackers gain complete access to router configuration including admin credentials, Wi-Fi passwords, port forwarding rules, and network topology, leading to full network compromise.
Likely Case
Attackers download configuration file containing admin credentials and network settings, enabling unauthorized access to router management interface and potential lateral movement.
If Mitigated
With proper network segmentation and firewall rules, impact limited to router compromise without access to internal systems.
🎯 Exploit Status
Exploit requires sending crafted HTTP request to vulnerable endpoint
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Unknown
Vendor Advisory: Not available
Restart Required: No
Instructions:
Check TOTOLINK website for firmware updates. If available, download latest firmware and upload via router admin interface.
🔧 Temporary Workarounds
Disable remote management
allTurn off remote administration access to router web interface
Restrict web interface access
allConfigure firewall to only allow trusted IPs to access router admin interface
🧯 If You Can't Patch
- Replace router with different model or manufacturer
- Isolate router on separate VLAN with strict firewall rules
🔍 How to Verify
Check if Vulnerable:
Attempt to access configuration file via HTTP request to router IP on vulnerable endpointCheck Version:
Login to router admin interface and check firmware version in System StatusVerify Fix Applied:
Test if configuration file download is no longer possible after firmware update📡 Detection & Monitoring
Log Indicators:
- HTTP requests to configuration file endpoints
- Unauthorized access to admin interface
Network Indicators:
- HTTP GET requests for config.bin or similar files
- Traffic to router on unusual ports
SIEM Query:
source_ip=external AND dest_ip=router_ip AND (uri_contains="config" OR uri_contains="backup")