CVE-2020-21650
📋 TL;DR
CVE-2020-21650 is a remote code execution vulnerability in Myucms v2.2.1 that allows attackers to execute arbitrary code on affected systems via the add() method in Config.php. This affects all users running Myucms v2.2.1, potentially compromising the entire web application and underlying server.
💻 Affected Systems
- Myucms
📦 What is this software?
Myucms by Myucms Project
⚠️ Risk & Real-World Impact
Worst Case
Complete system compromise allowing attackers to execute arbitrary commands, steal data, install malware, pivot to other systems, and maintain persistent access.
Likely Case
Web application takeover leading to data theft, defacement, or use as a foothold for further attacks within the network.
If Mitigated
Limited impact if proper network segmentation, WAF rules, and least privilege principles are implemented.
🎯 Exploit Status
Public exploit details available in GitHub issues. The vulnerability is in a core component and requires minimal technical skill to exploit.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Unknown
Vendor Advisory: No official vendor advisory found
Restart Required: No
Instructions:
1. Check if Myucms project has released an updated version. 2. If no patch exists, consider migrating to alternative software. 3. Apply workarounds immediately.
🔧 Temporary Workarounds
Restrict access to Config.php
allBlock direct access to the vulnerable Config.php file via web server configuration
For Apache: Add 'Deny from all' to .htaccess in controller directory
For Nginx: Add 'location ~* /controller/Config\.php { deny all; }' to site config
Input validation hardening
allAdd input validation to the add() method to prevent code injection
Modify controller/Config.php to validate and sanitize all user inputs before processing
🧯 If You Can't Patch
- Implement strict network segmentation to isolate the vulnerable system
- Deploy a web application firewall (WAF) with rules to block RCE attempts
🔍 How to Verify
Check if Vulnerable:
Check if Myucms version is 2.2.1 by examining the application files or configurationCheck Version:
Check the version in Myucms configuration files or application metadataVerify Fix Applied:
Test if the Config.php add() method properly validates inputs and prevents code execution📡 Detection & Monitoring
Log Indicators:
- Unusual POST requests to Config.php
- Suspicious PHP function calls in web logs
- Unexpected system command execution
Network Indicators:
- HTTP requests containing PHP code or system commands in parameters
- Outbound connections from web server to suspicious IPs
SIEM Query:
source="web_logs" AND (uri="*Config.php*" AND (method="POST" OR params="*system(*" OR params="*exec(*" OR params="*shell_exec(*"))