CVE-2023-40846
📋 TL;DR
CVE-2023-40846 is a critical buffer overflow vulnerability in Tenda AC6 routers that allows remote attackers to execute arbitrary code or cause denial of service. The vulnerability exists in the sub_90998 function of the firmware and affects users running vulnerable firmware versions. Attackers can exploit this without authentication to potentially take full control of affected routers.
💻 Affected Systems
- Tenda AC6 wireless router
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete compromise of router leading to network infiltration, credential theft, man-in-the-middle attacks, and persistent backdoor installation.
Likely Case
Router compromise allowing attackers to intercept traffic, modify DNS settings, or use the router as a pivot point into internal networks.
If Mitigated
Limited impact if network segmentation isolates routers and strict firewall rules prevent external access to management interfaces.
🎯 Exploit Status
Public proof-of-concept exists in GitHub repositories showing buffer overflow exploitation. The high CVSS score and public POC make weaponization likely.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Unknown
Vendor Advisory: No official vendor advisory found
Restart Required: Yes
Instructions:
1. Check Tenda website for firmware updates
2. If update available, download and flash via web interface
3. Factory reset after update
4. Reconfigure with secure settings
🔧 Temporary Workarounds
Disable remote management
allPrevent external access to router management interface
Change default admin credentials
allUse strong, unique passwords for router administration
🧯 If You Can't Patch
- Segment router on isolated network segment
- Implement strict firewall rules blocking all external access to router management ports
🔍 How to Verify
Check if Vulnerable:
Check router firmware version in web interface: System Tools > Firmware UpgradeCheck Version:
No CLI command available; use web interface at 192.168.0.1 or 192.168.1.1Verify Fix Applied:
Verify firmware version is newer than US_AC6V1.0BR_V15.03.05.16_multi_TD01.bin📡 Detection & Monitoring
Log Indicators:
- Unusual buffer overflow errors in router logs
- Multiple failed authentication attempts followed by successful login
Network Indicators:
- Unusual outbound connections from router
- DNS hijacking patterns
- Unexpected port scans originating from router
SIEM Query:
source="tenda-router" AND (event_type="buffer_overflow" OR auth_failure>5)