CVE-2023-39670
📋 TL;DR
This CVE describes a buffer overflow vulnerability in Tenda AC6 routers via the fgets function. Attackers can exploit this to execute arbitrary code or crash the device. Users of Tenda AC6 routers with the specified firmware version are affected.
💻 Affected Systems
- Tenda AC6 router
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Remote code execution leading to complete device compromise, network takeover, and lateral movement to connected devices.
Likely Case
Router crash causing denial of service, potentially requiring physical reset.
If Mitigated
Limited impact if network segmentation isolates the router and no sensitive traffic passes through it.
🎯 Exploit Status
Buffer overflow via fgets is a well-understood vulnerability type with public proof-of-concept available.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Unknown
Vendor Advisory: https://www.tendacn.com/download/list-3.html
Restart Required: Yes
Instructions:
1. Check vendor website for firmware updates. 2. Download latest firmware. 3. Upload via router admin interface. 4. Reboot router.
🔧 Temporary Workarounds
Disable remote management
allPrevents external exploitation by disabling WAN access to admin interface.
Login to router admin > Advanced > System Tools > Remote Management > Disable
Network segmentation
allIsolate router management interface to separate VLAN.
🧯 If You Can't Patch
- Replace vulnerable router with different model/brand
- Implement strict firewall rules blocking all unnecessary traffic to router
🔍 How to Verify
Check if Vulnerable:
Check router firmware version in admin interface under System Status or similar.Check Version:
Login to router web interface and navigate to System Status pageVerify Fix Applied:
Verify firmware version has changed from vulnerable version after update.📡 Detection & Monitoring
Log Indicators:
- Unusual crash/reboot logs
- Multiple failed login attempts to admin interface
Network Indicators:
- Unexpected traffic patterns to router management ports
- Malformed HTTP requests to router
SIEM Query:
source="router_logs" AND (event="crash" OR event="reboot")