CVE-2020-25414
📋 TL;DR
This vulnerability allows remote attackers to execute arbitrary PHP code through a local file inclusion flaw in Monstra CMS's captcha function. Attackers can potentially take full control of affected systems. All Monstra CMS 3.0.4 installations with the vulnerable captcha function are affected.
💻 Affected Systems
- Monstra CMS
📦 What is this software?
Monstra by Monstra
⚠️ Risk & Real-World Impact
Worst Case
Complete system compromise allowing remote code execution, data theft, defacement, and lateral movement within the network.
Likely Case
Website defacement, data exfiltration, and installation of backdoors or malware on the server.
If Mitigated
Limited impact if proper web application firewalls, file integrity monitoring, and least privilege principles are implemented.
🎯 Exploit Status
The vulnerability is well-documented in public GitHub issues with technical details that could be weaponized.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 3.0.5 or later
Vendor Advisory: https://github.com/monstra-cms/monstra/issues/469
Restart Required: No
Instructions:
1. Backup your current installation. 2. Download Monstra CMS 3.0.5 or later from the official repository. 3. Replace the vulnerable files with patched versions. 4. Verify the captcha functionality works correctly.
🔧 Temporary Workarounds
Disable captcha functionality
linuxTemporarily disable the vulnerable captcha module to prevent exploitation
# Remove or rename the captcha.php file in the vulnerable directory
mv /path/to/monstra/plugins/captcha/captcha.php /path/to/monstra/plugins/captcha/captcha.php.disabled
Implement WAF rules
allAdd web application firewall rules to block local file inclusion attempts
# Example ModSecurity rule to block LFI patterns
SecRule ARGS "\.\./" "phase:2,deny,id:1001,msg:'Local File Inclusion Attempt'
🧯 If You Can't Patch
- Implement strict input validation and sanitization for all user inputs
- Deploy a web application firewall with LFI protection rules
🔍 How to Verify
Check if Vulnerable:
Check if your Monstra installation is version 3.0.4 by examining the version file or admin panel. Review the captcha.php file for the vulnerable code pattern.Check Version:
cat /path/to/monstra/version.txt || grep 'version' /path/to/monstra/admin/index.phpVerify Fix Applied:
After patching, verify the version shows 3.0.5 or later. Test the captcha functionality to ensure it works without allowing file inclusion.📡 Detection & Monitoring
Log Indicators:
- Unusual file access patterns in web server logs
- Requests containing '../' or similar path traversal sequences
- Multiple failed captcha validation attempts
Network Indicators:
- Unusual outbound connections from the web server
- HTTP requests with suspicious parameters targeting captcha endpoints
SIEM Query:
source="web_server_logs" AND (uri="*captcha*" AND (param="*../*" OR param="*php://*"))