CVE-2020-27385
📋 TL;DR
This vulnerability allows authenticated attackers to read and write files outside the web root directory using directory traversal techniques in FlexDotnetCMS's FileEditor. Attackers can access sensitive system files by entering paths like ..\..\..\<file> or full paths like C:\<file>. All users running vulnerable versions of FlexDotnetCMS are affected.
💻 Affected Systems
- FlexDotnetCMS
📦 What is this software?
Flexdotnetcms by Flexdotnetcms Project
⚠️ Risk & Real-World Impact
Worst Case
Complete system compromise via reading/writing critical system files (e.g., /etc/passwd, SAM database), leading to credential theft, privilege escalation, or full system takeover.
Likely Case
Unauthorized access to sensitive configuration files, source code, or database credentials, potentially leading to data breaches or further system exploitation.
If Mitigated
Limited impact if proper file permissions and access controls prevent critical file modifications, though information disclosure may still occur.
🎯 Exploit Status
Exploitation is straightforward using directory traversal sequences in the FileEditor interface. Public blog posts demonstrate the technique.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: v1.5.11
Vendor Advisory: https://github.com/MacdonaldRobinson/FlexDotnetCMS/releases/tag/v1.5.11
Restart Required: Yes
Instructions:
1. Backup your current installation. 2. Download v1.5.11 from the GitHub releases page. 3. Replace existing files with patched version. 4. Restart the web application/service.
🔧 Temporary Workarounds
Disable FileEditor Access
allRemove or restrict access to the vulnerable FileEditor component
# Remove or rename the FileEditor directory
mv /path/to/FlexDotnetCMS/Admin/Views/FileEditor /path/to/FlexDotnetCMS/Admin/Views/FileEditor.disabled
# Or configure web server to block access to /Admin/Views/FileEditor/
Implement Web Application Firewall Rules
allBlock directory traversal patterns in requests
# Example mod_security rule for Apache
SecRule ARGS "\.\." "id:1001,phase:2,deny,msg:'Directory Traversal Attempt'"
# Example nginx rule
location ~* \.\. { deny all; }
🧯 If You Can't Patch
- Disable or restrict access to the FileEditor component entirely
- Implement strict file system permissions to limit what the web application user can access
🔍 How to Verify
Check if Vulnerable:
Check if you can access files outside web root by entering ..\..\..\..\windows\win.ini (Windows) or ../../../../etc/passwd (Linux) in the FileEditor path fieldCheck Version:
Check the CMS version in the admin panel or examine version files in the installation directoryVerify Fix Applied:
After patching, attempt the same directory traversal attacks - they should be blocked or return error messages📡 Detection & Monitoring
Log Indicators:
- Multiple failed attempts to access files with .. patterns
- Successful file access to paths outside normal web directories
- File modification timestamps on system files
Network Indicators:
- HTTP requests containing .. sequences to /Admin/Views/FileEditor/
- Unusual file read/write patterns from the web server
SIEM Query:
source="web_logs" AND (uri="/Admin/Views/FileEditor/" AND (request_body CONTAINS ".." OR uri CONTAINS ".."))