CVE-2023-1728
📋 TL;DR
CVE-2023-1728 is an unrestricted file upload vulnerability in Fernus Informatics LMS that allows attackers to upload malicious files, leading to OS command injection and server-side include injection. This affects all LMS installations before version 23.04.03, potentially giving attackers full control over affected systems.
💻 Affected Systems
- Fernus Informatics LMS
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete system compromise allowing remote code execution, data theft, lateral movement, and persistent backdoor installation.
Likely Case
Web server compromise leading to data exfiltration, defacement, or use as attack platform.
If Mitigated
Limited impact with proper file upload restrictions and web server hardening.
🎯 Exploit Status
Simple file upload bypass leads to RCE. Public exploit code exists in security advisories.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 23.04.03
Vendor Advisory: https://www.usom.gov.tr/bildirim/tr-23-0194
Restart Required: Yes
Instructions:
1. Download version 23.04.03 from official vendor source. 2. Backup current installation and data. 3. Stop LMS service. 4. Replace with patched version. 5. Restart service and verify functionality.
🔧 Temporary Workarounds
File Upload Restriction
allImplement strict file type validation and upload restrictions at web server level.
# Example nginx config: location ~ \.(php|sh|pl|py)$ { deny all; }
# Example Apache .htaccess: <FilesMatch "\.(php|sh|pl|py)$"> Order Allow,Deny Deny from all </FilesMatch>
Web Application Firewall Rules
allBlock malicious file upload patterns and suspicious file extensions.
# ModSecurity rule example: SecRule FILES_TMPNAMES "@rx \.(php|sh|pl|py)$" "id:1001,phase:2,deny"
🧯 If You Can't Patch
- Disable file upload functionality completely in LMS configuration.
- Implement network segmentation and restrict LMS access to trusted IPs only.
🔍 How to Verify
Check if Vulnerable:
Check LMS version in admin panel or configuration files. If version is below 23.04.03, system is vulnerable.Check Version:
Check admin panel or config files for version string. No universal CLI command available.Verify Fix Applied:
Verify version shows 23.04.03 or higher in admin interface and test file upload functionality with restricted extensions.📡 Detection & Monitoring
Log Indicators:
- Unusual file uploads with executable extensions
- Multiple failed upload attempts
- Web server error logs showing file execution attempts
Network Indicators:
- POST requests to upload endpoints with suspicious file names
- Outbound connections from web server to unknown IPs
SIEM Query:
source="web_logs" AND (url="*upload*" AND file_extension IN ("php", "sh", "pl", "py"))