CVE-2020-15568
📋 TL;DR
CVE-2020-15568 is a critical remote code execution vulnerability in TerraMaster TOS that allows attackers to execute arbitrary commands as root through improper parameter validation in the exportUser.php component. This affects all TerraMaster NAS devices running TOS versions before 4.1.29. Attackers can exploit this without authentication to gain complete control of affected systems.
💻 Affected Systems
- TerraMaster TOS (TerraMaster Operating System)
📦 What is this software?
Tos by Terra Master
⚠️ Risk & Real-World Impact
Worst Case
Complete system compromise with root-level access, allowing data theft, ransomware deployment, lateral movement to other systems, and persistent backdoor installation.
Likely Case
Remote attackers gain root shell access to install malware, exfiltrate sensitive data, or use the compromised device as a pivot point for further attacks.
If Mitigated
With proper network segmentation and access controls, impact is limited to the affected NAS device only, preventing lateral movement to other systems.
🎯 Exploit Status
Exploitation is straightforward with publicly available proof-of-concept code. The vulnerability allows direct command injection through HTTP parameters.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: TOS 4.1.29 and later
Vendor Advisory: https://help.terra-master.com/TOS/view/
Restart Required: Yes
Instructions:
1. Log into TerraMaster TOS web interface. 2. Navigate to Control Panel > General Settings > Update & Restore. 3. Check for updates and install TOS 4.1.29 or later. 4. Reboot the NAS after update completes.
🔧 Temporary Workarounds
Block access to exportUser.php
linuxTemporarily block web access to the vulnerable component using web server configuration or firewall rules.
# For Apache: add to .htaccess
<Files "exportUser.php">
Order Allow,Deny
Deny from all
</Files>
# For nginx: add to server block
location ~ /include/exportUser\.php$ {
deny all;
return 403;
}
Network isolation
allMove TerraMaster NAS to isolated VLAN with strict firewall rules limiting access to trusted IPs only.
🧯 If You Can't Patch
- Immediately disconnect affected devices from internet and restrict network access to administrative IPs only
- Implement strict network segmentation and monitor all traffic to/from TerraMaster devices for suspicious activity
🔍 How to Verify
Check if Vulnerable:
Check TOS version in web interface: Control Panel > General Settings > System Information. If version is below 4.1.29, device is vulnerable.Check Version:
# SSH into TerraMaster device and run:
cat /etc/version
# Or check via web API:
curl -k https://<nas-ip>/module/api.php?mobile/webNasIPSVerify Fix Applied:
After updating, verify version shows 4.1.29 or higher in System Information. Test that exportUser.php endpoint returns proper error or is inaccessible.📡 Detection & Monitoring
Log Indicators:
- HTTP requests to /include/exportUser.php with suspicious parameters
- Unusual process execution from web server user (www-data, apache, nginx)
- Multiple failed login attempts followed by successful access to exportUser.php
Network Indicators:
- HTTP POST requests to exportUser.php containing shell metacharacters or command strings
- Outbound connections from NAS to unusual external IPs or command-and-control servers
SIEM Query:
source="web_access_logs" AND (uri="/include/exportUser.php" OR uri="*exportUser*") AND (param="*exec*" OR param="*cmd*" OR param="*;*" OR param="*|*" OR param="*`*")