CVE-2021-46393
📋 TL;DR
This CVE describes a critical stack buffer overflow vulnerability in Tenda-AX3 routers that allows remote code execution. Attackers can exploit it by sending specially crafted HTTP POST requests to the router's web interface, potentially taking full control of the device. This affects Tenda-AX3 router users running the vulnerable firmware version.
💻 Affected Systems
- Tenda-AX3 router
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete compromise of the router allowing attackers to intercept all network traffic, install persistent malware, pivot to internal network devices, and use the router as part of a botnet.
Likely Case
Router takeover leading to DNS hijacking, credential theft from network traffic, and installation of backdoors for persistent access.
If Mitigated
Limited impact if the router is behind a firewall with restricted WAN access and web interface disabled.
🎯 Exploit Status
Public exploit code exists in GitHub repositories. The vulnerability requires no authentication and has a straightforward exploitation path.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Unknown
Vendor Advisory: No vendor advisory found
Restart Required: Yes
Instructions:
1. Check Tenda's official website for firmware updates
2. If available, download the latest firmware for AX3
3. Log into router admin interface
4. Navigate to System Tools > Firmware Upgrade
5. Upload and install the new firmware
6. Reboot the router
🔧 Temporary Workarounds
Disable Remote Management
allPrevent external access to the router's web interface
Change Default Admin Credentials
allUse strong, unique passwords for router administration
🧯 If You Can't Patch
- Replace the router with a different model/brand that receives security updates
- Place the router behind a separate firewall that blocks all inbound traffic to port 80/443
🔍 How to Verify
Check if Vulnerable:
Check router firmware version in admin interface. If version is V16.03.12.10_CN, the device is vulnerable.Check Version:
Log into router web interface and check System Status or Firmware Version pageVerify Fix Applied:
Verify firmware version has been updated to a version later than V16.03.12.10_CN📡 Detection & Monitoring
Log Indicators:
- HTTP POST requests to /goform/SetPptpServerCfg with long startIp parameter values
- Unusual process execution or memory errors in router logs
Network Indicators:
- Unusual outbound connections from router
- DNS queries to suspicious domains
- Unexpected port openings on router
SIEM Query:
source="router_logs" AND (uri="/goform/SetPptpServerCfg" OR method="POST" AND uri CONTAINS "SetPptpServerCfg")