CVE-2025-5851
📋 TL;DR
A critical buffer overflow vulnerability in Tenda AC15 routers allows remote attackers to execute arbitrary code by sending specially crafted HTTP POST requests to the /goform/AdvSetLanip endpoint. This affects Tenda AC15 routers running firmware version 15.03.05.19_multi. Attackers can exploit this without authentication to potentially take full control of affected devices.
💻 Affected Systems
- Tenda AC15
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Remote code execution leading to complete device compromise, lateral movement to internal networks, installation of persistent malware, and data exfiltration.
Likely Case
Device takeover leading to denial of service, network traffic interception, credential theft, and use as botnet node.
If Mitigated
Limited impact if device is behind firewall with restricted WAN access, though internal threats remain possible.
🎯 Exploit Status
Public exploit details are available, and the vulnerability requires minimal technical skill to exploit due to the straightforward buffer overflow in HTTP parameter handling.
🛠️ 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 AC15. 3. Access router admin interface. 4. Navigate to System Tools > Firmware Upgrade. 5. Upload and install new firmware. 6. Reboot router.
🔧 Temporary Workarounds
Disable Remote Management
allPrevent external access to router web interface
Access router admin > System Tools > Remote Management > Disable
Restrict LAN Access
linuxUse firewall rules to limit which internal hosts can access router management
iptables -A INPUT -p tcp --dport 80 -s 192.168.1.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 80 -j DROP
🧯 If You Can't Patch
- Replace vulnerable router with different model or updated version
- Place router behind dedicated firewall with strict inbound/outbound rules
🔍 How to Verify
Check if Vulnerable:
Check router firmware version in admin interface under System Status or System Tools > Firmware Upgrade pageCheck Version:
curl -s http://router-ip/goform/getStatus | grep version or check web interfaceVerify Fix Applied:
Verify firmware version is no longer 15.03.05.19_multi after update📡 Detection & Monitoring
Log Indicators:
- HTTP POST requests to /goform/AdvSetLanip with abnormal lanMask parameter length
- Router crash/reboot logs
- Unusual outbound connections from router
Network Indicators:
- HTTP traffic to router port 80 with POST to /goform/AdvSetLanip containing long strings in parameters
- Sudden router unresponsiveness followed by suspicious traffic
SIEM Query:
source="router_logs" AND (url="/goform/AdvSetLanip" AND method="POST" AND (param_length>100 OR status_code=500))