CVE-2025-5863
📋 TL;DR
This critical vulnerability in Tenda AC5 routers allows remote attackers to execute arbitrary code via a stack-based buffer overflow in the reboot timer function. Attackers can exploit this without authentication to potentially take full control of affected devices. All users running vulnerable firmware versions are at risk.
💻 Affected Systems
- Tenda AC5
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete device compromise leading to persistent backdoor installation, network traffic interception, lateral movement to other devices, and botnet recruitment.
Likely Case
Remote code execution allowing attackers to modify router settings, intercept 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 network attacks remain possible.
🎯 Exploit Status
Public exploit details available, making weaponization likely. Attack requires sending crafted HTTP request to vulnerable endpoint.
🛠️ 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 AC5 model
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
Network Segmentation
allIsolate router management interface to trusted network
🧯 If You Can't Patch
- Disable the router's web management interface entirely if not needed
- Implement strict firewall rules to block all external access to router management ports (80, 443, 8080)
🔍 How to Verify
Check if Vulnerable:
Check router firmware version in admin interface under System Status or System ToolsCheck Version:
curl -s http://router-ip/goform/getStatus | grep versionVerify Fix Applied:
Verify firmware version is newer than 15.03.06.47 after update📡 Detection & Monitoring
Log Indicators:
- HTTP POST requests to /goform/SetRebootTimer with unusually long rebootTime parameter
- Multiple failed authentication attempts followed by reboot timer requests
Network Indicators:
- Unusual outbound connections from router IP
- HTTP requests with buffer overflow patterns to router management port
SIEM Query:
source="router_logs" AND (uri="/goform/SetRebootTimer" AND content_length>100) OR (event="buffer_overflow" AND dest_ip="router_ip")