CVE-2021-41566
📋 TL;DR
CVE-2021-41566 is an unauthenticated remote code execution vulnerability in TadTools file upload functionality. Attackers can upload arbitrary files without authentication and execute malicious code on affected systems. This affects TadTools installations with vulnerable file upload components.
💻 Affected Systems
- TadTools
📦 What is this software?
Tadtools by Tadtools Project
⚠️ Risk & Real-World Impact
Worst Case
Complete system compromise allowing attackers to execute arbitrary commands, install malware, steal data, and pivot to other systems in the network.
Likely Case
Attackers upload web shells or malicious scripts to gain persistent access, deface websites, or deploy ransomware on vulnerable systems.
If Mitigated
With proper file extension filtering and authentication controls, the attack surface is significantly reduced, though other vulnerabilities might still exist.
🎯 Exploit Status
The vulnerability is straightforward to exploit - attackers simply need to craft a malicious file upload request without authentication.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Not explicitly stated in provided references, but patches should be available from TadTools developers.
Vendor Advisory: https://www.twcert.org.tw/tw/cp-132-5170-83472-1.html
Restart Required: No
Instructions:
1. Contact TadTools developers for the latest patched version. 2. Apply the security patch to fix file extension filtering. 3. Test the upload functionality to ensure proper filtering is implemented.
🔧 Temporary Workarounds
Implement Web Application Firewall (WAF)
allDeploy a WAF to block malicious file upload attempts and filter suspicious requests.
Disable File Upload Function
allTemporarily disable the vulnerable file upload functionality until patched.
🧯 If You Can't Patch
- Implement strict file extension whitelisting at the application level
- Add authentication requirements for all file upload operations
🔍 How to Verify
Check if Vulnerable:
Test if you can upload files with dangerous extensions (.php, .jsp, .asp, .exe) without authentication through TadTools upload function.Check Version:
Check TadTools version through administrative interface or configuration files specific to your installation.Verify Fix Applied:
After patching, attempt to upload files with dangerous extensions and verify they are rejected with proper error messages.📡 Detection & Monitoring
Log Indicators:
- Unusual file upload attempts, especially with executable extensions
- Multiple failed upload attempts from single IP
- Successful uploads of non-standard file types
Network Indicators:
- HTTP POST requests to upload endpoints with suspicious file names
- Traffic patterns showing file uploads without preceding authentication
SIEM Query:
source="web_server" AND (uri="*upload*" OR uri="*file*" OR method="POST") AND (filename="*.php" OR filename="*.jsp" OR filename="*.exe")