CVE-2020-20124
📋 TL;DR
CVE-2020-20124 is a remote code execution vulnerability in Wuzhi CMS v4.1.0 that allows attackers to execute arbitrary code on affected systems through the \attachment\admin\index.php file. This affects all users running the vulnerable version of Wuzhi CMS, potentially compromising entire websites and servers.
💻 Affected Systems
- Wuzhi CMS
📦 What is this software?
Wuzhicms by Wuzhicms
⚠️ Risk & Real-World Impact
Worst Case
Complete server takeover with data exfiltration, malware deployment, and persistent backdoor installation leading to full system compromise.
Likely Case
Website defacement, data theft, and installation of cryptocurrency miners or botnet clients on vulnerable servers.
If Mitigated
Limited impact with proper network segmentation, WAF rules, and minimal user privileges restricting lateral movement.
🎯 Exploit Status
Exploit code is publicly available and requires minimal technical skill to execute against vulnerable systems.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: v4.1.1 and later
Vendor Advisory: https://github.com/wuzhicms/wuzhicms/issues/188
Restart Required: No
Instructions:
1. Backup your current installation. 2. Download the latest version from the official repository. 3. Replace vulnerable files with patched versions. 4. Verify the fix by checking that \attachment\admin\index.php no longer accepts malicious input.
🔧 Temporary Workarounds
File Access Restriction
allBlock access to the vulnerable \attachment\admin\index.php file using web server configuration.
# Apache: Add to .htaccess
<Files "index.php">
Deny from all
</Files>
# Nginx: Add to server block
location ~ /attachment/admin/index\.php$ {
deny all;
}
Input Validation
allAdd input sanitization to prevent code execution in the vulnerable file.
# Add to index.php before any processing
if (isset($_GET['file'])) {
$file = basename($_GET['file']);
// Additional validation logic here
}
🧯 If You Can't Patch
- Implement strict network segmentation to isolate the vulnerable system from critical assets.
- Deploy a web application firewall (WAF) with rules to block RCE attempts targeting this specific vulnerability.
🔍 How to Verify
Check if Vulnerable:
Check if \attachment\admin\index.php exists and is accessible via HTTP request. Test with a harmless payload like 'echo test' if possible in a controlled environment.Check Version:
Check the version in the CMS admin panel or examine the version.txt file in the root directory.Verify Fix Applied:
Attempt to access the vulnerable endpoint with test payloads and verify they are blocked or sanitized. Check that the file has been updated to version 4.1.1 or later.📡 Detection & Monitoring
Log Indicators:
- Unusual POST/GET requests to \attachment\admin\index.php with suspicious parameters
- System commands execution in web server logs
- Unexpected process creation from web server user
Network Indicators:
- HTTP requests containing shell commands or encoded payloads targeting the vulnerable endpoint
- Outbound connections from web server to unknown IPs
SIEM Query:
source="web_server" AND (url="*attachment/admin/index.php*" AND (param="*system(*" OR param="*exec(*" OR param="*shell_exec(*"))