CVE-2025-6916
📋 TL;DR
This critical vulnerability in TOTOLINK T6 routers allows attackers to bypass authentication on the login form by manipulating authCode/goURL parameters. Attackers within the local network can gain unauthorized access to router administration. All users of affected TOTOLINK T6 routers with vulnerable firmware are at risk.
💻 Affected Systems
- TOTOLINK T6
📦 What is this software?
T6 Firmware by Totolink
⚠️ Risk & Real-World Impact
Worst Case
Complete router compromise allowing attacker to change network settings, intercept traffic, install malicious firmware, or use router as pivot point for attacking other internal devices.
Likely Case
Unauthorized administrative access to router configuration, enabling network reconnaissance, DNS hijacking, or credential theft from connected devices.
If Mitigated
Limited impact due to network segmentation, strong perimeter controls, and monitoring that detects authentication bypass attempts.
🎯 Exploit Status
Public exploit available on GitHub; simple HTTP request manipulation required; no authentication needed.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Unknown
Vendor Advisory: https://www.totolink.net/
Restart Required: Yes
Instructions:
1. Check TOTOLINK website for firmware updates. 2. Download latest firmware. 3. Access router admin panel. 4. Navigate to firmware upgrade section. 5. Upload new firmware file. 6. Wait for reboot.
🔧 Temporary Workarounds
Network Segmentation
allIsolate TOTOLINK T6 routers on separate VLAN to limit attack surface
Access Control Lists
linuxImplement firewall rules to restrict access to router admin interface
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 TOTOLINK T6 routers with different models or brands that have security updates
- Disable web administration interface and use only console/SSH management if supported
🔍 How to Verify
Check if Vulnerable:
Access router web interface, check firmware version in admin panel, compare with vulnerable version 4.1.5cu.748_B20211015Check Version:
curl -s http://router-ip/ | grep -i firmware || Check web interface admin panelVerify Fix Applied:
After firmware update, verify version changed from vulnerable version; test authentication bypass by attempting exploit📡 Detection & Monitoring
Log Indicators:
- Multiple failed login attempts followed by successful access
- Access to /formLoginAuth.htm with manipulated parameters
- Administrative configuration changes from unexpected IP addresses
Network Indicators:
- HTTP POST requests to /formLoginAuth.htm with authCode/goURL parameters
- Unusual traffic patterns to router admin interface
SIEM Query:
source="router.log" AND (url="/formLoginAuth.htm" AND (param="authCode" OR param="goURL"))