CVE-2026-3799
📋 TL;DR
A stack-based buffer overflow vulnerability in Tenda i3 routers allows remote attackers to execute arbitrary code by manipulating the funcpara1 parameter in the formSetCfm function. This affects Tenda i3 router users running vulnerable firmware. Remote exploitation is possible without authentication.
💻 Affected Systems
- Tenda i3 router
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Remote code execution leading to complete device compromise, network infiltration, and potential lateral movement to connected systems.
Likely Case
Router takeover enabling traffic interception, DNS manipulation, credential theft, and deployment of persistent malware.
If Mitigated
Limited impact if device is behind firewall with restricted WAN access, though internal network exposure remains.
🎯 Exploit Status
Public GitHub repository contains working exploit code with detailed instructions.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Unknown
Vendor Advisory: https://www.tenda.com.cn/
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
Network segmentation and firewall rules
allIsolate Tenda i3 routers from internet and restrict internal access
Disable remote administration
allTurn off WAN-side management access in router settings
🧯 If You Can't Patch
- Replace vulnerable Tenda i3 routers with different models or brands
- Implement strict network segmentation to isolate router from critical systems
🔍 How to Verify
Check if Vulnerable:
Access router admin interface and check firmware version matches 1.0.0.6(2204)Check Version:
Check router web interface or use nmap/router scanning toolsVerify Fix Applied:
Check firmware version is updated to a version later than 1.0.0.6(2204)📡 Detection & Monitoring
Log Indicators:
- Unusual POST requests to /goform/setcfm with manipulated funcpara1 parameter
- Router crash/reboot logs
Network Indicators:
- Exploit traffic patterns matching GitHub PoC
- Unusual outbound connections from router
SIEM Query:
source_ip=router AND uri_path="/goform/setcfm" AND http_method=POST AND contains(param, "funcpara1")