CVE-2023-39786
📋 TL;DR
This CVE describes a stack overflow vulnerability in Tenda AC8V4 routers via the time parameter in the sscanf function. Attackers can exploit this to execute arbitrary code or crash the device. Users of Tenda AC8V4 routers with vulnerable firmware are affected.
💻 Affected Systems
- Tenda AC8V4
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Remote code execution leading to complete device compromise, network infiltration, and persistent backdoor installation.
Likely Case
Device crash causing denial of service, potentially requiring physical reset.
If Mitigated
Limited impact with proper network segmentation and firewall rules preventing external access.
🎯 Exploit Status
Public GitHub repository contains proof-of-concept code demonstrating the vulnerability.
🛠️ 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. Access router admin interface. 4. Upload and apply firmware update. 5. Reboot router.
🔧 Temporary Workarounds
Disable remote management
allPrevent external access to router administration interface
Network segmentation
allIsolate router management interface to separate VLAN
🧯 If You Can't Patch
- Replace vulnerable router with different model or vendor
- Implement strict firewall rules blocking all external access to router management interface
🔍 How to Verify
Check if Vulnerable:
Access router admin interface, navigate to System Status or About page, check firmware version matches V16.03.34.06Check Version:
curl -s http://router-ip/status.cgi | grep versionVerify Fix Applied:
Check firmware version after update, verify it is newer than V16.03.34.06📡 Detection & Monitoring
Log Indicators:
- Multiple failed authentication attempts
- Unusual POST requests to time-related endpoints
- Router crash/reboot events
Network Indicators:
- Unusual traffic to router management port (typically 80/443)
- Exploit pattern matching in network traffic
SIEM Query:
source="router_logs" AND ("time parameter" OR "sscanf overflow" OR "firmware crash")