CVE-2023-38938
📋 TL;DR
This vulnerability is a stack overflow in Tenda routers' web interface that allows remote code execution. Attackers can exploit it by sending specially crafted requests to the /L7Im endpoint. Users of affected Tenda router models with vulnerable firmware versions are at risk.
💻 Affected Systems
- Tenda F1202
- Tenda PA202
- Tenda PW201A
- Tenda FH1202
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete device compromise allowing attacker to execute arbitrary code, steal credentials, pivot to internal networks, or create persistent backdoors.
Likely Case
Remote code execution leading to device takeover, network monitoring, or joining botnets.
If Mitigated
Limited impact if devices are behind firewalls with restricted WAN access and proper network segmentation.
🎯 Exploit Status
Public proof-of-concept available in GitHub repository. Exploitation requires network access to web interface.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Unknown
Vendor Advisory: Not available
Restart Required: Yes
Instructions:
1. Check Tenda website for firmware updates. 2. Download appropriate firmware for your model. 3. Access router web interface. 4. Navigate to firmware upgrade section. 5. Upload and apply new firmware. 6. Wait for router to reboot.
🔧 Temporary Workarounds
Disable WAN access to web interface
allPrevent external access to router management interface
Network segmentation
allIsolate affected routers from critical network segments
🧯 If You Can't Patch
- Replace affected devices with patched or different vendor models
- Implement strict firewall rules to block all traffic to router web interface from untrusted networks
🔍 How to Verify
Check if Vulnerable:
Check router firmware version via web interface or SSH if enabled. Compare against affected versions.Check Version:
curl -s http://router-ip/ | grep -i version or check web interface System Status pageVerify Fix Applied:
Verify firmware version has been updated to non-vulnerable version. Test if /L7Im endpoint still accepts malformed page parameter.📡 Detection & Monitoring
Log Indicators:
- Unusual POST requests to /L7Im endpoint
- Large page parameter values in requests
- Router crash/reboot logs
Network Indicators:
- HTTP requests to /L7Im with abnormal parameter lengths
- Traffic patterns suggesting exploit attempts
SIEM Query:
source="router-logs" AND (uri_path="/L7Im" OR (http_method="POST" AND uri_path CONTAINS "L7Im"))