CVE-2021-39503
📋 TL;DR
CVE-2021-39503 is a remote code execution vulnerability in PHPMyWind 5.6 that allows attackers to inject PHP code into configuration files due to insufficient input filtering. This affects all users running PHPMyWind 5.6, potentially giving attackers full control over affected web servers.
💻 Affected Systems
- PHPMyWind
📦 What is this software?
Phpmywind by Phpmywind
⚠️ Risk & Real-World Impact
Worst Case
Complete server compromise allowing attackers to execute arbitrary commands, steal data, install malware, or pivot to other systems.
Likely Case
Webshell deployment leading to data theft, defacement, or use as part of a botnet.
If Mitigated
Limited impact with proper web application firewalls and file integrity monitoring in place.
🎯 Exploit Status
Exploit requires specific input filtering bypass techniques
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Not available
Vendor Advisory: Not available
Restart Required: No
Instructions:
No official patch available. Consider upgrading to a different CMS or implementing workarounds.
🔧 Temporary Workarounds
Input Validation Enhancement
allAdd comprehensive input validation to WriteConfig() function to filter all special characters
Edit /include/config.cache.php and surrounding files to implement proper input sanitization
File Permissions Restriction
linuxSet strict file permissions on config.cache.php to prevent unauthorized writes
chmod 644 /include/config.cache.php
chown www-data:www-data /include/config.cache.php
🧯 If You Can't Patch
- Implement web application firewall (WAF) rules to block suspicious input patterns
- Monitor file integrity of /include/config.cache.php for unauthorized changes
🔍 How to Verify
Check if Vulnerable:
Check if PHPMyWind version is 5.6 and review WriteConfig() function for insufficient input filteringCheck Version:
Check PHPMyWind version in admin panel or readme filesVerify Fix Applied:
Test input validation by attempting to inject PHP code through vulnerable parameters📡 Detection & Monitoring
Log Indicators:
- Unusual file writes to /include/config.cache.php
- Suspicious POST requests with PHP code patterns
Network Indicators:
- HTTP requests containing PHP code snippets in parameters
SIEM Query:
source="web_logs" AND (uri_path="/include/config.cache.php" OR message="config.cache.php")