CVE-2020-19510
📋 TL;DR
CVE-2020-19510 is an arbitrary file upload vulnerability in Textpattern CMS that allows authenticated attackers to upload malicious files to the server. This affects Textpattern 4.7.3 installations where users have file upload privileges. Successful exploitation could lead to remote code execution.
💻 Affected Systems
- Textpattern CMS
📦 What is this software?
Textpattern by Textpattern
⚠️ Risk & Real-World Impact
Worst Case
Remote code execution leading to complete system compromise, data theft, and lateral movement within the network.
Likely Case
Webshell deployment allowing persistent backdoor access, data exfiltration, and further exploitation of the server.
If Mitigated
Limited impact if proper file type validation and upload restrictions are in place, potentially only file storage abuse.
🎯 Exploit Status
Exploitation requires authenticated access but is straightforward once credentials are obtained. Public proof-of-concept exists in the referenced blog posts.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Textpattern 4.8.0 and later
Vendor Advisory: https://textpattern.com/security/2020-19510
Restart Required: No
Instructions:
1. Backup your Textpattern installation and database. 2. Download Textpattern 4.8.0 or later from the official website. 3. Replace all files except /files, /images, and /textpattern/config.php. 4. Run the update script at /textpattern/index.php?event=prefs.
🔧 Temporary Workarounds
Restrict File Upload Permissions
allTemporarily disable or restrict file upload capabilities for non-admin users.
Edit user permissions in Textpattern admin panel to remove file upload rights
Web Server File Type Restrictions
linuxConfigure web server to block execution of uploaded files in upload directories.
For Apache: Add 'Options -ExecCGI' and 'RemoveHandler .php .php3 .php4 .php5 .php7 .phtml' to upload directory .htaccess
For Nginx: Add 'location ~ \.php$ { deny all; }' to upload directory configuration
🧯 If You Can't Patch
- Implement strict file type validation in the application layer to only allow specific safe file extensions.
- Move upload directory outside web root or configure web server to serve uploaded files as static content only.
🔍 How to Verify
Check if Vulnerable:
Check Textpattern version in admin panel or examine /textpattern/index.php for version information. Version 4.7.3 is vulnerable.Check Version:
Check /textpattern/index.php file header or admin dashboard for version information.Verify Fix Applied:
Verify version is 4.8.0 or later in admin panel. Test file upload functionality with malicious file extensions to ensure they are rejected.📡 Detection & Monitoring
Log Indicators:
- Unusual file uploads with executable extensions (.php, .php5, .phtml, etc.)
- Multiple failed upload attempts followed by successful upload
- Uploads from unusual user accounts or IP addresses
Network Indicators:
- HTTP POST requests to file upload endpoints with suspicious file contents
- Subsequent requests to uploaded files with executable extensions
SIEM Query:
source="web_logs" AND (uri_path="*file_insert*" OR uri_path="*upload*") AND (file_extension="php" OR file_extension="php5" OR file_extension="phtml")