CVE-2021-37221
📋 TL;DR
This vulnerability allows remote attackers to upload arbitrary PHP files through the account update and customer creation features in Sourcecodester Customer Relationship Management System 1.0. Successful exploitation could lead to remote code execution on the web server. Organizations using this specific CRM version are affected.
💻 Affected Systems
- Sourcecodester Customer Relationship Management System
📦 What is this software?
Customer Relationship Management System by Customer Relationship Management System Project
View all CVEs affecting Customer Relationship Management System →
⚠️ Risk & Real-World Impact
Worst Case
Complete system compromise via remote code execution, allowing attacker to execute arbitrary commands, steal data, install backdoors, or pivot to other systems.
Likely Case
Webshell deployment leading to data theft, defacement, or use as a foothold for further attacks within the network.
If Mitigated
Limited impact if file uploads are restricted to non-executable directories or proper file type validation is implemented.
🎯 Exploit Status
Exploit requires authentication but is trivial to execute once authenticated. Public exploit code is available.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Not available
Vendor Advisory: Not available
Restart Required: No
Instructions:
No official patch exists. Consider upgrading to a newer version if available or implementing workarounds.
🔧 Temporary Workarounds
File Upload Restriction
allImplement server-side file type validation to only allow specific non-executable file extensions.
Web Server Configuration
allConfigure web server to prevent execution of uploaded files in upload directories.
For Apache: Add 'php_flag engine off' to .htaccess in upload directory
For Nginx: Add 'location ~* \.php$ { deny all; }' to upload directory config
🧯 If You Can't Patch
- Implement web application firewall (WAF) rules to block file uploads with PHP extensions
- Restrict access to the CRM system to trusted IP addresses only
🔍 How to Verify
Check if Vulnerable:
Attempt to upload a PHP file through account update or customer creation features. If successful without validation, system is vulnerable.Check Version:
Check the CRM system version in the admin panel or about page.Verify Fix Applied:
Attempt to upload a PHP file - it should be rejected or saved in a non-executable manner.📡 Detection & Monitoring
Log Indicators:
- Unusual file uploads with .php extensions
- Multiple failed upload attempts followed by successful PHP file upload
- Web server logs showing execution of files from upload directories
Network Indicators:
- POST requests to upload endpoints with PHP file content
- Unusual outbound connections from web server after file upload
SIEM Query:
source="web_server" AND (uri="*update*" OR uri="*create*") AND method="POST" AND (file_extension=".php" OR content_type="application/x-php")