CVE-2020-17452
📋 TL;DR
This vulnerability allows authenticated administrators in flatCore CMS to upload and execute arbitrary PHP files, leading to remote code execution. It affects flatCore installations where admin accounts are compromised or misused. The vulnerability stems from insufficient file type validation in the upload functionality.
💻 Affected Systems
- flatCore CMS
📦 What is this software?
Flatcore by Flatcore
⚠️ Risk & Real-World Impact
Worst Case
Full server compromise through remote code execution, allowing attackers to steal data, install malware, or pivot to other systems.
Likely Case
Unauthorized PHP file upload leading to webshell installation and subsequent data exfiltration or system manipulation.
If Mitigated
Limited impact if proper file upload restrictions and admin account security are enforced.
🎯 Exploit Status
Exploitation requires admin credentials but is straightforward once authenticated. Public exploit details are available.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 1.5.7
Vendor Advisory: https://www.flatcore.org/
Restart Required: No
Instructions:
1. Backup your flatCore installation and database. 2. Download flatCore 1.5.7 or later from the official website. 3. Replace all files with the new version, preserving your configuration and content files. 4. Verify the update completed successfully.
🔧 Temporary Workarounds
Restrict PHP file uploads
allConfigure web server to block PHP file uploads or execution from upload directories
# For Apache: Add to .htaccess in upload directory
<Files *.php>
Order Deny,Allow
Deny from all
</Files>
# For Nginx: Add to server block
location ~* \.php$ {
deny all;
}
Implement file type validation
allAdd server-side validation to reject PHP file uploads
# Example PHP validation snippet
$allowed_types = ['image/jpeg', 'image/png', 'application/pdf'];
if (!in_array($_FILES['file']['type'], $allowed_types)) {
die('Invalid file type');
}
🧯 If You Can't Patch
- Implement strict admin account security with strong passwords and MFA
- Monitor upload directories for PHP files and implement file integrity monitoring
🔍 How to Verify
Check if Vulnerable:
Check flatCore version in admin panel or by examining core files. Versions below 1.5.7 are vulnerable.Check Version:
Check /acp/index.php or look for version information in flatCore configuration filesVerify Fix Applied:
Confirm version is 1.5.7 or higher in admin dashboard. Test PHP file upload functionality to ensure it's blocked.📡 Detection & Monitoring
Log Indicators:
- PHP file uploads to flatCore directories
- Unusual admin login activity
- File upload attempts with .php extension
Network Indicators:
- POST requests to upload endpoints with PHP files
- Unusual outbound connections from web server
SIEM Query:
source="web_logs" AND (uri_path="/acp/core/mediamgr.php" OR uri_path="/acp/core/upload.php") AND file_extension=".php"