CVE-2021-41919
📋 TL;DR
CVE-2021-41919 is an unrestricted file upload vulnerability in webTareas that allows authenticated users to upload dangerous files via the profile picture upload functionality. This enables attackers to upload malicious code that could lead to remote code execution or client-side attacks. All users of webTareas version 2.4 and earlier are affected.
💻 Affected Systems
- webTareas
📦 What is this software?
Webtareas by Webtareas Project
⚠️ Risk & Real-World Impact
Worst Case
Remote code execution on the server, complete system compromise, and malware distribution to users through malicious file uploads.
Likely Case
Malicious file upload leading to client-side attacks, session hijacking, or limited server compromise depending on file execution context.
If Mitigated
File uploads restricted to safe types with proper validation, limiting impact to denial of service or minor data exposure.
🎯 Exploit Status
Exploitation requires authenticated access but is straightforward via HTTP POST requests to the vulnerable endpoint.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Version 2.5 or later
Vendor Advisory: https://n4nj0.github.io/advisories/webtareas-multiple-vulnerabilities-i/
Restart Required: No
Instructions:
1. Upgrade webTareas to version 2.5 or later. 2. Verify the patch implements proper file type validation and restrictions on uploads.
🔧 Temporary Workarounds
Web Server File Restriction
allConfigure web server to block access to /includes/upload.php or restrict file uploads via .htaccess or equivalent.
# Apache .htaccess example
<Files "upload.php">
Order Allow,Deny
Deny from all
</Files>
WAF Rule Implementation
allDeploy web application firewall rules to block malicious file uploads to the vulnerable endpoint.
# ModSecurity rule example
SecRule REQUEST_URI "@contains /includes/upload.php" \
"id:1001,phase:2,deny,msg:'Blocking CVE-2021-41919 exploit attempt'"
🧯 If You Can't Patch
- Implement strict file upload validation on the application layer, allowing only specific safe file types (e.g., .jpg, .png).
- Deploy network segmentation to isolate the webTareas instance and restrict access to authenticated users only.
🔍 How to Verify
Check if Vulnerable:
Attempt to upload a non-image file (e.g., .php, .exe) via the profile picture upload feature at /includes/upload.php.Check Version:
Check webTareas version in the application interface or configuration files.Verify Fix Applied:
Test that only allowed file types (images) can be uploaded and that malicious file extensions are rejected.📡 Detection & Monitoring
Log Indicators:
- HTTP POST requests to /includes/upload.php with non-image file extensions
- Large or unusual file uploads to the upload endpoint
Network Indicators:
- Unusual traffic patterns to /includes/upload.php
- File uploads with executable extensions
SIEM Query:
source="web_server" AND uri="/includes/upload.php" AND (file_extension="php" OR file_extension="exe" OR file_extension="js")