CVE-2021-46062
📋 TL;DR
MCMS v5.2.5 contains an arbitrary file deletion vulnerability via the oldFileName component. This allows attackers to delete arbitrary files on the server, potentially causing denial of service or data loss. Any system running the vulnerable MCMS version is affected.
💻 Affected Systems
- MCMS
📦 What is this software?
Mcms by Mingsoft
⚠️ Risk & Real-World Impact
Worst Case
Complete system compromise through deletion of critical system files, leading to permanent data loss, system instability, or complete service disruption.
Likely Case
Deletion of web application files causing service disruption, loss of user data, or defacement of websites.
If Mitigated
Limited impact if proper file permissions and input validation are in place, potentially only affecting non-critical files.
🎯 Exploit Status
The GitHub issue shows exploitation details, making weaponization likely. Authentication may be required depending on configuration.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: v5.2.6 or later
Vendor Advisory: https://github.com/ming-soft/MCMS/issues/59
Restart Required: Yes
Instructions:
1. Backup your current installation and database. 2. Download the latest MCMS version from the official repository. 3. Replace the vulnerable files with patched versions. 4. Restart the web server and application services.
🔧 Temporary Workarounds
Input Validation Filter
allAdd input validation to restrict file paths that can be deleted
Modify the oldFileName component to validate file paths against an allowlist
File Permission Restriction
linuxSet strict file permissions to limit what files the web user can delete
chmod 644 for web files, chmod 755 for directories, restrict web user to specific directories
🧯 If You Can't Patch
- Implement strict file system permissions to limit the web application user's access
- Deploy a web application firewall (WAF) with rules to block file deletion attempts
🔍 How to Verify
Check if Vulnerable:
Check if MCMS version is 5.2.5 by examining version files or configurationCheck Version:
Check the version.txt file or MCMS admin panel for version informationVerify Fix Applied:
Verify installation of MCMS v5.2.6 or later and test file deletion functionality📡 Detection & Monitoring
Log Indicators:
- Unusual file deletion events in web server logs
- Multiple failed file deletion attempts
- Requests to oldFileName with suspicious parameters
Network Indicators:
- HTTP requests containing file paths in oldFileName parameter
- Unusual patterns of file operation requests
SIEM Query:
source="web_server" AND (uri="*oldFileName*" OR method="DELETE") AND status="200"