CVE-2025-65222
📋 TL;DR
Tenda AC21 router firmware version V16.03.08.16 contains a buffer overflow vulnerability in the rebootTime parameter of the /goform/SetSysAutoRebbotCfg endpoint. This allows attackers to potentially execute arbitrary code or crash the device. Only users running this specific firmware version on Tenda AC21 routers are affected.
💻 Affected Systems
- Tenda AC21
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Remote code execution leading to complete device compromise, persistent backdoor installation, or router becoming part of botnet
Likely Case
Device crash requiring physical reboot, temporary denial of service for connected users
If Mitigated
No impact if device is patched or network segmentation prevents access to management interface
🎯 Exploit Status
Public GitHub repository contains proof-of-concept. Exploitation appears straightforward based on available information.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Unknown
Vendor Advisory: Unknown
Restart Required: Yes
Instructions:
1. Check Tenda website for firmware updates
2. Download latest firmware for AC21
3. Access router admin panel
4. Navigate to System Tools > Firmware Upgrade
5. Upload new firmware file
6. Wait for automatic reboot
🔧 Temporary Workarounds
Disable Remote Management
allPrevent external access to router management interface
Network Segmentation
allIsolate router management interface to separate VLAN
🧯 If You Can't Patch
- Replace affected router with different model or vendor
- Implement strict firewall rules blocking all access to router management interface from untrusted networks
🔍 How to Verify
Check if Vulnerable:
Access router web interface, navigate to System Status page and check firmware version matches V16.03.08.16Check Version:
curl -s http://router-ip/goform/getStatus | grep versionVerify Fix Applied:
After firmware update, verify version no longer shows V16.03.08.16📡 Detection & Monitoring
Log Indicators:
- Multiple POST requests to /goform/SetSysAutoRebbotCfg with long rebootTime parameters
- Router crash/reboot logs
Network Indicators:
- Unusual HTTP POST traffic to router management port (typically 80/443)
- Large payloads sent to /goform/SetSysAutoRebbotCfg endpoint
SIEM Query:
source="router_logs" AND (url="/goform/SetSysAutoRebbotCfg" OR message="reboot" OR message="crash")