CVE-2020-22755
📋 TL;DR
MCMS 5.0 contains a file upload vulnerability that allows attackers to upload malicious files disguised as thumbnails, leading to arbitrary code execution. This affects all systems running MCMS 5.0 with file upload functionality enabled. Attackers can compromise the entire system through this vulnerability.
💻 Affected Systems
- MCMS (MingSoft Content Management System)
📦 What is this software?
Mcms by Mingsoft
⚠️ Risk & Real-World Impact
Worst Case
Complete system compromise with remote code execution, data theft, and potential lateral movement within the network.
Likely Case
Webshell deployment leading to data exfiltration, defacement, or use as a foothold for further attacks.
If Mitigated
Limited impact with proper file upload restrictions and web application firewalls in place.
🎯 Exploit Status
The vulnerability is well-documented in GitHub issues and requires minimal technical skill to exploit.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Version after 5.0 (check latest release)
Vendor Advisory: https://github.com/ming-soft/MCMS/issues/42
Restart Required: Yes
Instructions:
1. Backup your current installation. 2. Download the latest version from the official GitHub repository. 3. Replace vulnerable files with patched versions. 4. Restart the web server. 5. Verify the fix by testing file upload functionality.
🔧 Temporary Workarounds
Disable File Upload
allTemporarily disable thumbnail/file upload functionality in MCMS
Modify MCMS configuration to remove file upload endpoints
Web Application Firewall Rules
allImplement WAF rules to block malicious file uploads
Configure WAF to block file uploads with executable extensions
Implement file type validation at the WAF level
🧯 If You Can't Patch
- Implement strict file upload validation (allow only specific image formats, verify file signatures)
- Deploy a web application firewall with specific rules to block malicious file uploads
🔍 How to Verify
Check if Vulnerable:
Check if running MCMS version 5.0. Attempt to upload a file with executable extension disguised as an image.Check Version:
Check MCMS configuration files or admin panel for version informationVerify Fix Applied:
After patching, attempt to upload malicious files and verify they are rejected. Check that only legitimate image files are accepted.📡 Detection & Monitoring
Log Indicators:
- Unusual file upload activity
- Uploads of non-image files to thumbnail endpoints
- Multiple failed upload attempts
Network Indicators:
- HTTP POST requests to file upload endpoints with suspicious content
- Traffic patterns indicating file upload exploitation
SIEM Query:
source="web_server" AND (uri_path="*upload*" OR uri_path="*thumbnail*") AND (file_extension="php" OR file_extension="jsp" OR file_extension="asp")