CVE-2025-14656
📋 TL;DR
A buffer overflow vulnerability in Tenda AC20 routers allows remote attackers to execute arbitrary code by manipulating schedStartTime/schedEndTime parameters in the openSchedWifi function. This affects Tenda AC20 routers running firmware version 16.03.08.12. Attackers can exploit this from the internet 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, lateral movement to internal networks, persistent backdoor installation, and botnet recruitment.
Likely Case
Remote code execution allowing attackers to modify router settings, intercept network traffic, or use the device as a pivot point for further attacks.
If Mitigated
Limited impact if device is behind firewall with restricted WAN access, though internal threats remain possible.
🎯 Exploit Status
Public exploit code is available on GitHub. 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 AC20. 3. Log into 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
Log into router admin > Advanced > System Tools > Remote Management > Disable
Restrict WAN Access
linuxBlock external access to router management ports
iptables -A INPUT -p tcp --dport 80 -j DROP
iptables -A INPUT -p tcp --dport 443 -j DROP
🧯 If You Can't Patch
- Isolate affected routers in separate VLAN with strict firewall rules
- Implement network segmentation to limit lateral movement potential
🔍 How to Verify
Check if Vulnerable:
Check router firmware version in 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 newer than 16.03.08.12 and test if openSchedWifi endpoint still accepts malformed input📡 Detection & Monitoring
Log Indicators:
- Multiple POST requests to /goform/openSchedWifi with unusually long parameters
- HTTP requests containing buffer overflow patterns in schedStartTime/schedEndTime
Network Indicators:
- Unusual outbound connections from router IP
- Traffic patterns suggesting command and control communication
SIEM Query:
source="router_logs" AND uri="/goform/openSchedWifi" AND (param_length>100 OR contains(param,"schedStartTime") OR contains(param,"schedEndTime"))