CVE-2015-9551
📋 TL;DR
This vulnerability allows remote attackers to execute arbitrary commands on affected TOTOLINK routers via the management interface's sysCmd parameter. It affects TOTOLINK A850R-V1 and F1-V2 devices with specific firmware versions. Attackers can gain full control of the device without authentication.
💻 Affected Systems
- TOTOLINK A850R-V1
- TOTOLINK F1-V2
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete device takeover allowing attackers to install persistent malware, intercept all network traffic, pivot to internal networks, or use the device as part of a botnet.
Likely Case
Attackers gain shell access to execute commands, potentially modifying device configuration, stealing credentials, or launching attacks against internal systems.
If Mitigated
If the management interface is not exposed to the internet and network segmentation is in place, risk is limited to internal attackers with network access.
🎯 Exploit Status
Exploitation requires sending a crafted HTTP POST request to the vulnerable endpoint with command injection in the sysCmd parameter.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Unknown
Vendor Advisory: None available
Restart Required: No
Instructions:
No official patch available. Consider replacing affected devices with supported models.
🔧 Temporary Workarounds
Disable WAN access to management interface
allPrevent external access to the vulnerable management interface
Access router admin panel → Security/Firewall → Disable remote management/WAN access
Change default credentials
allUse strong, unique passwords for router administration
Access router admin panel → System/Management → Change admin password
🧯 If You Can't Patch
- Isolate affected routers in a separate VLAN with strict firewall rules
- Implement network monitoring for suspicious traffic to/from router management ports
🔍 How to Verify
Check if Vulnerable:
Check firmware version in router web interface: System → Firmware Upgrade → Current VersionCheck Version:
curl -s http://router-ip/cgi-bin/cstecgi.cgi | grep versionVerify Fix Applied:
Verify management interface is not accessible from WAN by testing from external network📡 Detection & Monitoring
Log Indicators:
- HTTP POST requests to /cgi-bin/cstecgi.cgi containing sysCmd parameter
- Unusual command execution in system logs
Network Indicators:
- External IP addresses accessing router management port (typically 80/8080)
- HTTP traffic containing command injection patterns
SIEM Query:
source="router.log" AND "sysCmd" AND ("|" OR ";" OR "$" OR "`")