CVE-2025-11385
📋 TL;DR
A buffer overflow vulnerability in Tenda AC20 routers allows remote attackers to execute arbitrary code by manipulating the timeZone parameter. This affects Tenda AC20 routers up to firmware version 16.03.08.12. Attackers can exploit this without authentication to potentially take full control of affected devices.
💻 Affected Systems
- Tenda AC20
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Remote code execution leading to complete device compromise, persistent backdoor installation, and lateral movement into internal networks.
Likely Case
Router compromise allowing traffic interception, DNS hijacking, credential theft, and botnet recruitment.
If Mitigated
Limited impact if devices are behind firewalls with strict inbound filtering and network segmentation.
🎯 Exploit Status
Proof-of-concept exploit code is publicly available on GitHub. The vulnerability requires no authentication and has straightforward exploitation.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Unknown
Vendor Advisory: Not available
Restart Required: Yes
Instructions:
1. Check Tenda's official website for firmware updates. 2. Download the latest firmware for AC20. 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
Disable Remote Management
allPrevent external access to the router's web interface
Network Segmentation
allIsolate router management interface to separate VLAN
🧯 If You Can't Patch
- Block inbound access to router web interface (ports 80/443) at network perimeter
- Replace vulnerable devices with supported models from different vendors
🔍 How to Verify
Check if Vulnerable:
Check firmware version in router admin interface under System Status or System Tools > Firmware UpgradeCheck Version:
curl -s http://router-ip/goform/getStatus | grep versionVerify Fix Applied:
Verify firmware version is higher than 16.03.08.12 after update📡 Detection & Monitoring
Log Indicators:
- Unusual POST requests to /goform/fast_setting_wifi_set with long timeZone parameters
- Multiple failed exploit attempts
Network Indicators:
- Unusual outbound connections from router
- DNS queries to known malicious domains
SIEM Query:
source="router_logs" AND uri="/goform/fast_setting_wifi_set" AND (timeZone.length > 50 OR status=500)