CVE-2023-39784
📋 TL;DR
This vulnerability allows remote attackers to execute arbitrary code on Tenda AC8V4 routers via a stack overflow in the save_virtualser_data function. Attackers can exploit this by sending specially crafted requests to the vulnerable parameter. All users running the affected firmware version are at risk.
💻 Affected Systems
- Tenda AC8V4
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete device compromise leading to persistent backdoor installation, network traffic interception, and lateral movement to other devices on the network.
Likely Case
Remote code execution allowing attackers to modify router settings, intercept traffic, or use the device as part of a botnet.
If Mitigated
Limited impact if device is behind firewall with restricted WAN access and proper network segmentation.
🎯 Exploit Status
Public exploit code available on GitHub. No authentication required for exploitation.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Unknown
Vendor Advisory: http://tenda.com
Restart Required: Yes
Instructions:
1. Check Tenda website for firmware updates. 2. Download latest firmware. 3. Log into router admin panel. 4. Navigate to System Tools > Firmware Upgrade. 5. Upload and install new firmware. 6. Reboot router.
🔧 Temporary Workarounds
Disable Remote Management
allPrevent external access to router web interface
Log into router admin > Advanced > System Tools > Remote Management > Disable
Restrict Management Interface Access
allLimit which IPs can access router management
Log into router admin > Advanced > Security > Access Control > Add allowed IPs only
🧯 If You Can't Patch
- Place router behind firewall with strict inbound rules blocking all WAN access to management ports
- Segment router on isolated VLAN with no access to critical internal resources
🔍 How to Verify
Check if Vulnerable:
Check firmware version in router admin panel under System Status or System ToolsCheck Version:
curl -s http://router-ip/goform/getStatus | grep versionVerify Fix Applied:
Verify firmware version is newer than V16.03.34.06📡 Detection & Monitoring
Log Indicators:
- Unusual POST requests to /goform/saveVirtualserData
- Multiple failed exploitation attempts
- Unexpected router reboots
Network Indicators:
- Unusual outbound connections from router
- Traffic to known C2 servers
- Port scanning originating from router
SIEM Query:
source="router.log" AND ("saveVirtualserData" OR "list parameter overflow")