CVE-2020-15488
📋 TL;DR
CVE-2020-15488 is an insecure file upload vulnerability in Re:Desk 2.3 help desk software that allows attackers to upload malicious files without proper validation. This affects all organizations running Re:Desk 2.3, potentially leading to remote code execution or server compromise. The vulnerability stems from insufficient file type and content validation in upload functionality.
💻 Affected Systems
- Re:Desk
📦 What is this software?
Re\ by Re Desk
⚠️ Risk & Real-World Impact
Worst Case
Remote code execution leading to complete system compromise, data theft, ransomware deployment, or creation of persistent backdoors on the server.
Likely Case
Upload of web shells or malicious scripts enabling unauthorized access, data exfiltration, or lateral movement within the network.
If Mitigated
Limited impact with proper file validation and execution restrictions, potentially only allowing denial of service through storage exhaustion.
🎯 Exploit Status
The vulnerability requires no authentication and has simple exploitation steps. Public advisories include technical details that facilitate exploitation.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 2.4 or later
Vendor Advisory: https://www.re-desk.com/download-help-desk-software.html
Restart Required: Yes
Instructions:
1. Download Re:Desk 2.4 or later from the official website. 2. Backup your current installation and database. 3. Stop the Re:Desk service. 4. Install the new version following vendor instructions. 5. Restart the service and verify functionality.
🔧 Temporary Workarounds
Web Server File Upload Restrictions
allConfigure web server to block uploads of executable file types
# For Apache: Add to .htaccess
<FilesMatch "\.(php|phtml|php3|php4|php5|pl|py|jsp|asp|sh|cgi)$">
Order Allow,Deny
Deny from all
</FilesMatch>
# For Nginx: Add to server block
location ~* \.(php|phtml|php3|php4|php5|pl|py|jsp|asp|sh|cgi)$ {
deny all;
}
File Upload Directory Isolation
linuxMove upload directory outside web root and restrict permissions
# Move upload directory
mv /var/www/redesk/uploads /var/uploads_redesk
# Set restrictive permissions
chmod 750 /var/uploads_redesk
chown www-data:www-data /var/uploads_redesk
🧯 If You Can't Patch
- Implement web application firewall (WAF) rules to block malicious file uploads based on file signatures and extensions
- Disable file upload functionality entirely if not required for business operations
🔍 How to Verify
Check if Vulnerable:
Check if running Re:Desk version 2.3 by examining version files or admin interface. Attempt to upload a file with executable extension (.php, .jsp, etc.) to test if validation is missing.Check Version:
Check admin interface or examine version.txt in installation directoryVerify Fix Applied:
After patching, verify version is 2.4 or later. Test file upload functionality with various file types to ensure proper validation is in place.📡 Detection & Monitoring
Log Indicators:
- Unusual file uploads with executable extensions
- Multiple failed upload attempts
- Uploads from unexpected IP addresses
- Files with suspicious names (e.g., shell.php, cmd.jsp)
Network Indicators:
- POST requests to upload endpoints with executable file content
- Unusual outbound connections from the Re:Desk server after file uploads
SIEM Query:
source="redesk_logs" AND (url_path="*upload*" OR method="POST") AND (file_extension="php" OR file_extension="jsp" OR file_extension="asp" OR file_extension="py")