CVE-2021-45740
📋 TL;DR
This vulnerability is a stack overflow in the setWiFiWpsStart function of TOTOLINK A720R routers. Attackers can send specially crafted pin parameter values to cause a Denial of Service (DoS), potentially crashing the device. This affects users running the vulnerable firmware version on TOTOLINK A720R routers.
💻 Affected Systems
- TOTOLINK A720R
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete device crash requiring physical reboot, potential remote code execution if stack overflow can be controlled to execute arbitrary code.
Likely Case
Router becomes unresponsive, requiring reboot to restore WiFi and network services.
If Mitigated
Limited to DoS if proper input validation is implemented, but device may still require reboot.
🎯 Exploit Status
Public proof-of-concept available on GitHub. Exploitation requires sending crafted HTTP request to vulnerable endpoint.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Unknown
Vendor Advisory: Unknown
Restart Required: Yes
Instructions:
1. Check TOTOLINK website for firmware updates
2. Download latest firmware for A720R
3. Access router admin interface
4. Navigate to firmware upgrade section
5. Upload and apply new firmware
6. Reboot router
🔧 Temporary Workarounds
Disable WPS
allDisable WiFi Protected Setup feature to prevent access to vulnerable function
Restrict Management Interface
allConfigure firewall to restrict access to router management interface
🧯 If You Can't Patch
- Isolate router on separate network segment
- Implement strict network access controls to router management interface
🔍 How to Verify
Check if Vulnerable:
Check router firmware version in admin interface. If version is v4.1.5cu.470_B20200911, device is vulnerable.Check Version:
Check router web interface or use nmap/router scanning toolsVerify Fix Applied:
Verify firmware version has been updated to a version later than v4.1.5cu.470_B20200911📡 Detection & Monitoring
Log Indicators:
- Multiple failed WPS connection attempts
- Router crash/reboot logs
- Unusual HTTP requests to management interface
Network Indicators:
- HTTP POST requests to router management interface with long pin parameters
- Sudden loss of router connectivity
SIEM Query:
source="router_logs" AND (event="WPS_start" OR event="crash")