CVE-2025-4849
📋 TL;DR
This critical vulnerability in TOTOLINK N300RH routers allows remote attackers to execute arbitrary commands through command injection in the CloudACMunualUpdateUserdata function. Attackers can exploit this by manipulating the 'url' parameter in the /cgi-bin/cstecgi.cgi endpoint. All users of affected TOTOLINK N300RH routers with vulnerable firmware are at risk.
💻 Affected Systems
- TOTOLINK N300RH
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete device compromise allowing attackers to install persistent backdoors, steal credentials, pivot to internal networks, or use the device for botnet activities.
Likely Case
Remote code execution leading to device takeover, credential harvesting, and potential lateral movement within the network.
If Mitigated
Limited impact if device is behind strict firewall rules, has network segmentation, and proper monitoring in place.
🎯 Exploit Status
Public exploit code is available on GitHub, making exploitation straightforward for attackers with basic skills.
🛠️ 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 update section. 5. Upload and apply new firmware. 6. Reboot router.
🔧 Temporary Workarounds
Network Isolation
allIsolate affected routers from critical networks and internet exposure
Access Control
linuxRestrict access to router admin interface using firewall rules
iptables -A INPUT -p tcp --dport 80 -s TRUSTED_IP -j ACCEPT
iptables -A INPUT -p tcp --dport 80 -j DROP
🧯 If You Can't Patch
- Replace affected routers with supported models from different vendors
- Implement strict network segmentation to isolate vulnerable devices
🔍 How to Verify
Check if Vulnerable:
Check router firmware version in admin interface under System Status or Firmware Update sectionCheck Version:
curl -s http://router-ip/cgi-bin/cstecgi.cgi | grep -i versionVerify Fix Applied:
Verify firmware version has been updated to a version newer than 6.1c.1390_B20191101📡 Detection & Monitoring
Log Indicators:
- Unusual CGI requests to /cgi-bin/cstecgi.cgi with suspicious URL parameters
- Multiple failed login attempts followed by successful CGI access
- Commands like 'wget', 'curl', or 'sh' in URL parameters
Network Indicators:
- Unusual outbound connections from router to unknown IPs
- Traffic patterns suggesting command-and-control communication
- Port scanning originating from router
SIEM Query:
source="router_logs" AND (uri="/cgi-bin/cstecgi.cgi" AND (url="*;*" OR url="*|*" OR url="*`*"))