CVE-2025-55824
📋 TL;DR
ModStartCMS v9.5.0 contains an arbitrary file write vulnerability that allows attackers to upload malicious files to the server. This can lead to remote code execution and compromise of sensitive server data. All users running the vulnerable version are affected.
💻 Affected Systems
- ModStartCMS
📦 What is this software?
Mostartcms by Modstart
⚠️ Risk & Real-World Impact
Worst Case
Full server compromise with attacker gaining shell access, data exfiltration, and persistent backdoor installation
Likely Case
Webshell deployment leading to data theft, defacement, or use as attack pivot
If Mitigated
Limited impact with proper file permission restrictions and web application firewalls
🎯 Exploit Status
Exploit requires understanding of file upload mechanisms but no authentication bypass needed
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: v9.5.1 or later
Vendor Advisory: https://modstart.com/
Restart Required: No
Instructions:
1. Backup current installation. 2. Download latest version from official ModStartCMS website. 3. Replace vulnerable files with patched version. 4. Verify file permissions are properly set.
🔧 Temporary Workarounds
Restrict File Upload Permissions
allConfigure web server to prevent execution of uploaded files in upload directories
chmod 644 /path/to/upload/directory/*
find /path/to/upload -type f -name '*.php' -delete
🧯 If You Can't Patch
- Implement strict file upload validation in application code
- Deploy web application firewall with file upload protection rules
🔍 How to Verify
Check if Vulnerable:
Check if running ModStartCMS v9.5.0 by examining version.php or admin panelCheck Version:
grep -r 'version' /path/to/modstart/version.phpVerify Fix Applied:
Verify version is updated to v9.5.1+ and test file upload functionality with malicious payloads📡 Detection & Monitoring
Log Indicators:
- Unusual file uploads to upload directories
- PHP file creation in non-standard locations
- Webshell access patterns
Network Indicators:
- POST requests with file uploads to vulnerable endpoints
- Unusual outbound connections from web server
SIEM Query:
source="web_logs" AND (uri="/upload" OR uri="/admin/upload") AND file_extension="php"