CVE-2020-19551
📋 TL;DR
This vulnerability allows attackers to bypass file upload blacklists in WUZHI CMS, potentially leading to remote code execution. It affects all WUZHI CMS installations up to version 4.1.0. Attackers can upload malicious files that execute arbitrary code on the server.
💻 Affected Systems
- WUZHI CMS
📦 What is this software?
Wuzhicms by Wuzhicms
⚠️ Risk & Real-World Impact
Worst Case
Full server compromise allowing attackers to execute arbitrary commands, steal data, install backdoors, or pivot to other systems.
Likely Case
Webshell deployment leading to data theft, defacement, or use as part of a botnet.
If Mitigated
Limited impact with proper file upload restrictions and web application firewalls in place.
🎯 Exploit Status
Exploitation requires file upload access, which may need authentication depending on configuration.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Version 4.1.1 or later
Vendor Advisory: https://github.com/wuzhicms/wuzhicms/issues/177
Restart Required: No
Instructions:
1. Backup your current installation. 2. Download WUZHI CMS 4.1.1 or later from the official repository. 3. Replace the vulnerable common.func.php file with the patched version. 4. Verify the fix by testing file upload functionality.
🔧 Temporary Workarounds
Disable File Uploads
allTemporarily disable file upload functionality until patching is complete.
Modify CMS configuration to disable uploads or restrict to trusted users only
Implement Strict File Type Validation
allAdd server-side validation to only allow specific safe file types.
Add MIME type and extension validation in upload handling code
🧯 If You Can't Patch
- Implement web application firewall (WAF) rules to block malicious file uploads
- Restrict file upload permissions to specific trusted users only
🔍 How to Verify
Check if Vulnerable:
Check if your WUZHI CMS version is 4.1.0 or earlier by examining the version file or admin panel.Check Version:
Check the version.txt file or login to admin panel to see version informationVerify Fix Applied:
Verify the common.func.php file has been updated to version 4.1.1 or later and test file upload functionality with restricted file types.📡 Detection & Monitoring
Log Indicators:
- Unusual file uploads, especially with executable extensions
- Multiple failed upload attempts followed by successful upload
Network Indicators:
- HTTP POST requests to upload endpoints with unusual file types
- Subsequent connections to uploaded files
SIEM Query:
source="web_server" AND (method="POST" AND uri="*upload*" AND (file_extension="php" OR file_extension="jsp" OR file_extension="asp"))