CVE-2021-43484
📋 TL;DR
This vulnerability allows unauthenticated attackers to execute arbitrary code on Simple Client Management System 1.0 servers by uploading malicious files through create.php. Any organization using this software without proper file extension validation is affected.
💻 Affected Systems
- Simple Client Management System
📦 What is this software?
Simple Client Management System by Simple Client Management System Project
⚠️ Risk & Real-World Impact
Worst Case
Complete system compromise leading to data theft, ransomware deployment, or creation of persistent backdoors.
Likely Case
Webshell installation allowing unauthorized access, data exfiltration, and lateral movement within the network.
If Mitigated
Limited impact with proper network segmentation and file upload restrictions.
🎯 Exploit Status
Exploit code is publicly available and requires minimal technical skill to execute.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: N/A
Vendor Advisory: N/A
Restart Required: No
Instructions:
No official patch exists. Consider migrating to alternative software or implementing workarounds.
🔧 Temporary Workarounds
File Upload Restriction
allImplement server-side validation to restrict file uploads to specific extensions
Modify create.php to validate file extensions before processing
Web Application Firewall Rule
allBlock requests to create.php with suspicious file extensions
WAF rule: Block POST requests to */create.php containing .php, .phtml, .phar extensions
🧯 If You Can't Patch
- Remove or disable create.php functionality entirely
- Implement strict network segmentation to isolate the vulnerable system
🔍 How to Verify
Check if Vulnerable:
Check if Simple Client Management System version 1.0 is installed and create.php exists without file extension validationCheck Version:
Check application files for version information or review installation documentationVerify Fix Applied:
Test file upload functionality with malicious extensions to confirm they are rejected📡 Detection & Monitoring
Log Indicators:
- Multiple failed/successful file upload attempts to create.php
- Unusual POST requests to create.php with executable extensions
Network Indicators:
- HTTP POST requests to create.php with .php/.phtml files
- Outbound connections from web server to unknown IPs
SIEM Query:
source="web_logs" AND uri="*/create.php" AND (file_extension="php" OR file_extension="phtml")