CVE-2026-3380
📋 TL;DR
This vulnerability allows remote attackers to execute arbitrary code on Tenda F453 routers by exploiting a buffer overflow in the frmL7ImForm function. Attackers can launch attacks over the network without authentication, potentially taking full control of affected devices. Users of Tenda F453 routers with firmware version 1.0.0.3 are affected.
💻 Affected Systems
- Tenda F453
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete device compromise allowing attackers to install persistent malware, intercept network traffic, pivot to internal networks, or brick the device.
Likely Case
Remote code execution leading to device takeover, network surveillance, or participation in botnets.
If Mitigated
Limited impact if devices are behind firewalls with strict inbound filtering and network segmentation.
🎯 Exploit Status
Public exploit code exists in GitHub repositories. The vulnerability is in a web form handler, making exploitation straightforward for attackers with network access.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Unknown
Vendor Advisory: https://www.tenda.com.cn/
Restart Required: Yes
Instructions:
1. Check Tenda's official website for firmware updates. 2. Download the latest firmware for F453. 3. Log into router admin interface. 4. Navigate to System Tools > Firmware Upgrade. 5. Upload and install the new firmware. 6. Reboot the router.
🔧 Temporary Workarounds
Block Web Management Interface
linuxPrevent external access to the router's web interface using firewall rules.
iptables -A INPUT -p tcp --dport 80 -j DROP
iptables -A INPUT -p tcp --dport 443 -j DROP
Change Default Management Port
allModify the router's web interface to use a non-standard port.
🧯 If You Can't Patch
- Isolate the router on a separate VLAN with strict access controls
- Implement network monitoring for unusual traffic patterns to/from the router
🔍 How to Verify
Check if Vulnerable:
Check router firmware version in web interface: System Status > Firmware Version. If version is 1.0.0.3, device is vulnerable.Check Version:
curl -s http://router-ip/ | grep -i 'firmware version' or check web interfaceVerify Fix Applied:
After firmware update, verify version is no longer 1.0.0.3. Test if /goform/L7Im endpoint still responds with buffer overflow payloads.📡 Detection & Monitoring
Log Indicators:
- Unusual POST requests to /goform/L7Im with long parameter values
- Multiple failed login attempts followed by buffer overflow patterns
Network Indicators:
- Unusual outbound connections from router to unknown IPs
- Traffic patterns suggesting command and control communication
SIEM Query:
source="router_logs" AND (uri="/goform/L7Im" AND content_length>1000) OR (http_method="POST" AND uri CONTAINS "L7Im")