CVE-2025-4851
📋 TL;DR
This critical vulnerability in TOTOLINK N300RH routers allows remote attackers to execute arbitrary commands by manipulating the FileName parameter in the setUploadUserData function. Attackers can exploit this command injection flaw to gain control of affected devices. All users running vulnerable firmware versions are at risk.
💻 Affected Systems
- TOTOLINK N300RH
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete device compromise allowing persistent backdoor installation, network traffic interception, lateral movement to other devices, and participation in botnets.
Likely Case
Remote code execution leading to device takeover, credential theft, and network reconnaissance.
If Mitigated
Limited impact if devices are behind firewalls with strict inbound filtering and network segmentation.
🎯 Exploit Status
Exploit details are publicly available on GitHub. The vulnerability requires no authentication and has simple exploitation vectors.
🛠️ 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 interface. 4. Navigate to firmware upgrade section. 5. Upload and apply new firmware. 6. Reboot router.
🔧 Temporary Workarounds
Network Access Restriction
linuxBlock external access to router management interface
iptables -A INPUT -p tcp --dport 80 -j DROP
iptables -A INPUT -p tcp --dport 443 -j DROP
Disable Remote Management
allTurn off remote administration features in router settings
🧯 If You Can't Patch
- Isolate affected routers in separate VLAN with strict firewall rules
- Implement network monitoring for unusual outbound connections from routers
🔍 How to Verify
Check if Vulnerable:
Check router firmware version in admin interface. If version is 6.1c.1390_B20191101, device is vulnerable.Check Version:
curl -s http://router-ip/cgi-bin/cstecgi.cgi | grep version or check web interfaceVerify Fix Applied:
After firmware update, verify version has changed from vulnerable version. Test if exploit payloads no longer work.📡 Detection & Monitoring
Log Indicators:
- Unusual POST requests to /cgi-bin/cstecgi.cgi with FileName parameter containing shell metacharacters
- Failed authentication attempts followed by command injection attempts
Network Indicators:
- HTTP requests containing shell commands in parameters
- Unusual outbound connections from router to external IPs
SIEM Query:
source="router_logs" AND uri="/cgi-bin/cstecgi.cgi" AND (FileName="*;*" OR FileName="*|*" OR FileName="*`*" OR FileName="*$(*")