CVE-2021-4462
📋 TL;DR
CVE-2021-4462 is an unrestricted file upload vulnerability in Employee Records System version 1.0 that allows remote unauthenticated attackers to upload arbitrary files via uploadID.php. This leads to remote code execution since uploaded files can be executed without proper server-side validation. Any organization using this vulnerable version is affected.
💻 Affected Systems
- Employee Records System
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete system compromise with attacker gaining full control over the server, data exfiltration, ransomware deployment, and lateral movement to other systems.
Likely Case
Remote code execution leading to web shell installation, data theft, and potential use as a foothold for further attacks.
If Mitigated
Attack blocked at perimeter with no successful exploitation due to proper file validation and access controls.
🎯 Exploit Status
Exploitation observed in the wild by Shadowserver Foundation; simple HTTP POST request with malicious file payload.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Not available
Vendor Advisory: Not available
Restart Required: No
Instructions:
1. Remove or disable the vulnerable Employee Records System installation. 2. Replace with alternative software or custom-developed solution with proper security controls.
🔧 Temporary Workarounds
Disable uploadID.php endpoint
allBlock access to the vulnerable upload endpoint via web server configuration
# Apache: RewriteRule ^uploadID\.php$ - [F,L]
# Nginx: location ~ /uploadID\.php$ { return 403; }
Implement file upload restrictions
allAdd server-side validation to restrict file types and extensions
# Add to uploadID.php: $allowed_extensions = ['jpg', 'png', 'pdf']; $file_extension = strtolower(pathinfo($_FILES['file']['name'], PATHINFO_EXTENSION)); if (!in_array($file_extension, $allowed_extensions)) { die('Invalid file type'); }
🧯 If You Can't Patch
- Isolate the system on a separate network segment with strict firewall rules
- Implement web application firewall (WAF) with file upload protection rules
🔍 How to Verify
Check if Vulnerable:
Check if Employee Records System version 1.0 is installed and accessible; attempt to upload a test file (e.g., test.php) to /uploadID.php endpoint.Check Version:
Check application files for version information; typically in README or configuration files.Verify Fix Applied:
Attempt to upload malicious file types (.php, .exe) to verify they are rejected; check that only allowed file types are accepted.📡 Detection & Monitoring
Log Indicators:
- HTTP POST requests to /uploadID.php with unusual file extensions (.php, .exe, .jsp)
- Files with suspicious names uploaded to upload directories
- Unusual process execution from web directories
Network Indicators:
- Outbound connections from web server to unknown IPs
- Unusual traffic patterns from the affected system
SIEM Query:
source="web_server_logs" AND (uri="/uploadID.php" AND method="POST" AND (user_agent CONTAINS "curl" OR user_agent CONTAINS "wget" OR file_extension IN ("php", "exe", "jsp")))