CVE-2021-45996
📋 TL;DR
This CVE describes a stack overflow vulnerability in Tenda G1 and G3 routers that allows attackers to cause Denial of Service (DoS) by sending specially crafted requests to the formSetPortMapping function. The vulnerability affects routers with specific firmware versions and can be exploited remotely without authentication. Attackers can crash the router's web interface or potentially execute arbitrary code.
💻 Affected Systems
- Tenda G1 Router
- Tenda G3 Router
📦 What is this software?
G1 Firmware by Tendacn
G3 Firmware by Tendacn
⚠️ Risk & Real-World Impact
Worst Case
Remote code execution leading to complete router compromise, persistent backdoor installation, and network infiltration.
Likely Case
Denial of Service causing router reboot or web interface crash, disrupting network connectivity.
If Mitigated
Limited impact with proper network segmentation and firewall rules blocking external access to router management interface.
🎯 Exploit Status
Public proof-of-concept code exists in GitHub repositories. Exploitation requires sending crafted HTTP POST requests to the vulnerable endpoint.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Unknown - Check Tenda website for latest firmware
Vendor Advisory: Not publicly documented
Restart Required: Yes
Instructions:
1. Log into Tenda router admin interface. 2. Navigate to System Tools > Firmware Upgrade. 3. Download latest firmware from Tenda official website. 4. Upload and install firmware update. 5. Reboot router after installation.
🔧 Temporary Workarounds
Disable Remote Management
allPrevent external access to router web interface
Block Port Forwarding Access
linuxUse firewall rules to restrict access to router management ports
iptables -A INPUT -p tcp --dport 80 -j DROP
iptables -A INPUT -p tcp --dport 443 -j DROP
🧯 If You Can't Patch
- Isolate router on separate VLAN with strict access controls
- Implement network monitoring for abnormal HTTP requests to router management interface
🔍 How to Verify
Check if Vulnerable:
Check router firmware version in admin interface under System Status or System ToolsCheck Version:
curl -s http://router-ip/goform/getStatus | grep versionVerify Fix Applied:
Verify firmware version has been updated to newer than v15.11.0.17(9502)_CN📡 Detection & Monitoring
Log Indicators:
- Multiple POST requests to /goform/setPortMapping
- Router reboot logs
- Web interface crash events
Network Indicators:
- Unusual HTTP traffic to router port 80/443 with long parameter values
- Multiple connection attempts to router management interface
SIEM Query:
source="router.log" AND ("setPortMapping" OR "formSetPortMapping") AND (POST)