CVE-2023-40915
📋 TL;DR
This vulnerability in Tenda AX3 routers allows attackers to trigger a stack buffer overflow via the ssid parameter in the form_fast_setting_wifi_set function, leading to Denial of Service (DoS). Attackers can crash the device remotely, disrupting network connectivity. Users running Tenda AX3 firmware version 16.03.12.11 are affected.
💻 Affected Systems
- Tenda AX3
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Remote code execution leading to complete device compromise, persistent backdoor installation, or permanent bricking of the router.
Likely Case
Remote Denial of Service causing router crash and network downtime until manual reboot.
If Mitigated
Limited to DoS with quick recovery if proper network segmentation and monitoring are in place.
🎯 Exploit Status
Public proof-of-concept exists in GitHub repositories. Exploitation requires sending a crafted HTTP request to the router's web interface.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Unknown
Vendor Advisory: Not available
Restart Required: Yes
Instructions:
1. Check Tenda's official website for firmware updates. 2. 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 by disabling remote administration.
Network Segmentation
allIsolate the router management interface to a dedicated VLAN with restricted access.
🧯 If You Can't Patch
- Replace the vulnerable router with a different model or from a different vendor.
- Implement strict firewall rules to block all external access to the router's web management port (typically TCP 80/443).
🔍 How to Verify
Check if Vulnerable:
Check router firmware version in admin interface under System Status or similar. If version is 16.03.12.11, it is vulnerable.Check Version:
Log into router web interface and navigate to System Status page, or use curl: curl -s http://router-ip/status.cgi | grep versionVerify Fix Applied:
After updating firmware, verify the version has changed from 16.03.12.11 to a newer version.📡 Detection & Monitoring
Log Indicators:
- Unusual HTTP POST requests to /goform/fast_setting_wifi_set with long ssid parameters
- Router crash/reboot logs
Network Indicators:
- Multiple HTTP requests to router management interface with abnormal payload lengths
- Sudden loss of connectivity to router
SIEM Query:
source="router_logs" AND (uri_path="/goform/fast_setting_wifi_set" AND content_length>1000)