CVE-2025-3820
📋 TL;DR
A critical stack-based buffer overflow vulnerability in Tenda W12 and i24 routers allows remote attackers to execute arbitrary code by manipulating hostIp1/hostIp2 parameters in the cgiSysUplinkCheckSet function. This affects routers running vulnerable firmware versions, potentially giving attackers full control of affected devices.
💻 Affected Systems
- Tenda W12
- Tenda i24
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Remote code execution leading to complete device compromise, persistent backdoor installation, network traffic interception, and lateral movement to other devices on the network.
Likely Case
Remote code execution resulting in device takeover, botnet enrollment, credential theft, and network disruption.
If Mitigated
Limited impact if devices are behind firewalls with strict inbound filtering and network segmentation.
🎯 Exploit Status
Exploit details have been publicly disclosed on GitHub, making weaponization likely. The vulnerability requires no authentication and has straightforward exploitation.
🛠️ 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 for your model. 3. Access router admin interface. 4. Navigate to firmware upgrade section. 5. Upload and apply new firmware. 6. Reboot router.
🔧 Temporary Workarounds
Network Segmentation and Firewall Rules
linuxIsolate routers from untrusted networks and restrict access to management interfaces.
iptables -A INPUT -p tcp --dport 80 -s TRUSTED_NETWORK -j ACCEPT
iptables -A INPUT -p tcp --dport 80 -j DROP
🧯 If You Can't Patch
- Replace affected routers with different models or brands that are not vulnerable
- Implement strict network segmentation to isolate routers from critical assets
🔍 How to Verify
Check if Vulnerable:
Check router firmware version in admin interface. If version is 3.0.0.4(2887) or 3.0.0.5(3644), device is vulnerable.Check Version:
Login to router admin interface and check System Status or Firmware Version page.Verify Fix Applied:
Verify firmware version has been updated to a version later than 3.0.0.5(3644) and check that the /bin/httpd binary has been replaced.📡 Detection & Monitoring
Log Indicators:
- Unusual HTTP requests to /cgi-bin/luci/ with hostIp parameters
- Multiple failed buffer overflow attempts in system logs
- Unexpected process creation from httpd
Network Indicators:
- Unusual outbound connections from router to unknown IPs
- Traffic patterns suggesting command and control communication
- Port scanning originating from router
SIEM Query:
source="router_logs" AND (uri="/cgi-bin/luci/*" AND (hostIp1 OR hostIp2)) OR process="httpd" AND action="execve"