CVE-2021-42123
📋 TL;DR
This vulnerability allows authenticated users with upload privileges to upload files of any type to the TopEase platform. Attackers can upload malicious files like HTML pages with JavaScript or executable scripts, enabling client-side attacks against other users. Organizations running TopEase Platform Version 7.1.27 or earlier are affected.
💻 Affected Systems
- Business-DNA Solutions GmbH TopEase Platform
📦 What is this software?
Topease by Businessdnasolutions
⚠️ Risk & Real-World Impact
Worst Case
Attackers upload malicious HTML/JavaScript files that execute in victims' browsers, leading to session hijacking, credential theft, or drive-by malware infections when users access uploaded content.
Likely Case
Attackers upload phishing pages or malicious scripts that steal session cookies or credentials from authenticated users who view uploaded files.
If Mitigated
With proper file type validation and content inspection, malicious uploads are blocked, limiting impact to legitimate file operations only.
🎯 Exploit Status
Exploitation requires authenticated access but is technically simple once credentials are obtained.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Version 7.1.28 or later
Vendor Advisory: https://confluence.topease.ch/confluence/display/DOC/Release+Notes
Restart Required: Yes
Instructions:
1. Download TopEase Platform Version 7.1.28 or later from vendor portal. 2. Backup current installation and data. 3. Apply the update following vendor upgrade procedures. 4. Restart TopEase services.
🔧 Temporary Workarounds
Implement file type validation
allConfigure web application firewall or application controls to restrict uploads to approved file types only
Restrict upload privileges
allLimit upload functionality to minimal necessary users and implement role-based access controls
🧯 If You Can't Patch
- Implement strict file type validation at the application layer to only allow specific safe extensions
- Store uploaded files outside web root with unique names and serve through secure download handlers
🔍 How to Verify
Check if Vulnerable:
Check TopEase version in administration panel; if version is 7.1.27 or earlier, system is vulnerable.Check Version:
Check TopEase web interface administration section or consult platform documentation for version command.Verify Fix Applied:
After patching, verify version shows 7.1.28 or later in administration panel and test file upload with restricted types.📡 Detection & Monitoring
Log Indicators:
- Unusual file uploads with non-standard extensions
- Multiple upload attempts from single user
- Uploads of HTML, JS, or executable file types
Network Indicators:
- HTTP POST requests to upload endpoints with suspicious file types
- Subsequent requests to access uploaded files with unusual extensions
SIEM Query:
source="topease" AND (event="file_upload" AND file_extension NOT IN ("pdf","doc","jpg","png"))