CVE-2023-31903
📋 TL;DR
GuppY CMS 6.00.10 contains an unrestricted file upload vulnerability that allows remote attackers to upload PHP files and execute arbitrary code on the server. This affects all systems running the vulnerable version of GuppY CMS. Attackers can gain complete control of affected web servers.
💻 Affected Systems
- GuppY CMS
📦 What is this software?
Guppy by Freeguppy
⚠️ Risk & Real-World Impact
Worst Case
Complete server compromise leading to data theft, ransomware deployment, lateral movement within the network, and persistent backdoor installation.
Likely Case
Webshell installation leading to data exfiltration, website defacement, and use as a pivot point for further attacks.
If Mitigated
Attack blocked at web application firewall level with file upload restrictions preventing PHP execution.
🎯 Exploit Status
Multiple public exploits exist with simple upload mechanisms. No authentication required for exploitation.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Not available
Vendor Advisory: Not available
Restart Required: No
Instructions:
1. Check if newer versions of GuppY CMS exist. 2. If no patch exists, implement workarounds immediately. 3. Consider migrating to a maintained CMS platform.
🔧 Temporary Workarounds
Restrict file upload extensions
allConfigure web server to block PHP file uploads and execution from upload directories
# Apache: Add to .htaccess in upload directory
<Files *.php>
Order Deny,Allow
Deny from all
</Files>
# Nginx: Add to server block
location ~* \.php$ {
deny all;
return 403;
}
Implement file type validation
allAdd server-side validation to reject PHP files and check MIME types
# PHP validation example
$allowed_extensions = array('jpg', 'png', 'gif', 'pdf');
$file_extension = strtolower(pathinfo($filename, PATHINFO_EXTENSION));
if (!in_array($file_extension, $allowed_extensions)) {
die('Invalid file type');
}
🧯 If You Can't Patch
- Implement web application firewall (WAF) rules to block PHP file uploads
- Isolate the vulnerable system in a DMZ with strict network segmentation
🔍 How to Verify
Check if Vulnerable:
Attempt to upload a PHP file with simple content like <?php echo 'test'; ?> to any upload functionality. If the file uploads successfully and can be accessed via URL, the system is vulnerable.Check Version:
Check GuppY CMS version in admin panel or look for version information in source code commentsVerify Fix Applied:
Attempt the same PHP file upload test. The upload should be rejected or the file should not be executable when accessed via URL.📡 Detection & Monitoring
Log Indicators:
- Multiple failed upload attempts followed by successful PHP file upload
- Access to unusual file extensions in upload directories
- POST requests to upload endpoints with PHP content
Network Indicators:
- HTTP POST requests with PHP file uploads to upload endpoints
- Subsequent HTTP GET requests to uploaded PHP files
SIEM Query:
source="web_logs" (method="POST" AND uri="*upload*" AND (file_extension="php" OR content_type="application/x-php")) OR (method="GET" AND uri="*/uploads/*.php")