CVE-2020-21250
📋 TL;DR
CVE-2020-21250 is an arbitrary file upload vulnerability in CSZ CMS v1.2.4 that allows attackers to upload malicious files to the server. This affects all systems running the vulnerable version of CSZ CMS, potentially leading to complete system compromise.
💻 Affected Systems
- CSZ CMS
📦 What is this software?
Csz Cms by Cszcms
⚠️ Risk & Real-World Impact
Worst Case
Full remote code execution leading to complete server takeover, data exfiltration, and lateral movement within the network.
Likely Case
Webshell deployment allowing persistent backdoor access, data theft, and further exploitation of the server.
If Mitigated
Limited impact if file uploads are restricted to authenticated users and proper file validation is implemented.
🎯 Exploit Status
The vulnerability is in the file upload mechanism and requires minimal technical skill to exploit.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: v1.2.5 or later
Vendor Advisory: https://github.com/cskaza/cszcms/issues/22
Restart Required: No
Instructions:
1. Backup your current installation. 2. Download the latest version from the official repository. 3. Replace the vulnerable files with patched versions. 4. Verify the fix by testing file upload functionality.
🔧 Temporary Workarounds
Disable file upload functionality
allTemporarily disable file uploads in the CMS configuration or via .htaccess rules
# Add to .htaccess: RewriteRule ^core/MY_Security.php - [F,L]
Implement file type restrictions
allAdd server-side validation to restrict uploads to specific file types
# In PHP configuration or application code, restrict uploads to specific extensions
🧯 If You Can't Patch
- Implement web application firewall (WAF) rules to block malicious file uploads
- Restrict access to the vulnerable endpoint using network access controls
🔍 How to Verify
Check if Vulnerable:
Check if running CSZ CMS version 1.2.4 by examining the version file or admin panelCheck Version:
grep -r 'version' /path/to/cszcms/ or check admin dashboardVerify Fix Applied:
Verify version is 1.2.5 or later and test file upload functionality with malicious files📡 Detection & Monitoring
Log Indicators:
- Unusual file uploads to /core/MY_Security.php
- Uploads of executable files (php, exe, etc.)
- Multiple failed upload attempts
Network Indicators:
- POST requests to /core/MY_Security.php with file uploads
- Unusual outbound connections after file uploads
SIEM Query:
source="web_logs" AND uri="/core/MY_Security.php" AND method="POST" AND (file_extension="php" OR file_extension="exe" OR file_extension="sh")