CVE-2023-39827
📋 TL;DR
This vulnerability allows remote attackers to execute arbitrary code on Tenda A18 routers by exploiting a stack overflow in the MAC filter rule management function. Attackers can send specially crafted requests to the vulnerable endpoint, potentially gaining full control of affected devices. This affects all users running the vulnerable firmware version.
💻 Affected Systems
- Tenda A18 WiFi Router
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete device compromise leading to persistent backdoor installation, network traffic interception, credential theft, and lateral movement to other network devices.
Likely Case
Router takeover allowing attackers to modify network settings, intercept traffic, deploy malware to connected devices, or use the router as part of a botnet.
If Mitigated
Limited impact if device is behind firewall with restricted WAN access, though internal network attacks remain possible.
🎯 Exploit Status
Public proof-of-concept code exists in GitHub repositories. The stack overflow appears to be straightforward to exploit for remote code execution.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Unknown
Vendor Advisory: Not found
Restart Required: Yes
Instructions:
1. Check Tenda website for firmware updates. 2. If update available, download and install via web interface. 3. Factory reset after update to ensure clean state. 4. Monitor for official patch release.
🔧 Temporary Workarounds
Disable Remote Management
allTurn off remote administration/management features to prevent external exploitation
Network Segmentation
allIsolate router management interface to separate VLAN with restricted access
🧯 If You Can't Patch
- Replace affected router with different model/brand that receives security updates
- Place router behind dedicated firewall with strict inbound rules blocking all unnecessary ports
🔍 How to Verify
Check if Vulnerable:
Check router firmware version in web interface (typically at 192.168.0.1 or 192.168.1.1) under System Status or About pageCheck Version:
curl -s http://router-ip/goform/getStatus | grep version (if API accessible)Verify Fix Applied:
Verify firmware version is newer than V15.13.07.09 after update📡 Detection & Monitoring
Log Indicators:
- Unusual POST requests to /goform/AddMacfilterRule
- Multiple failed MAC filter rule additions
- Router crash/reboot logs
Network Indicators:
- Unusual traffic patterns from router to external IPs
- Router initiating unexpected outbound connections
- MAC filter rule changes from unauthorized sources
SIEM Query:
source="router_logs" AND (uri="/goform/AddMacfilterRule" OR rule_info="*overflow*")