CVE-2020-28063
📋 TL;DR
CVE-2020-28063 is a critical file upload vulnerability in ArticleCMS that allows attackers to upload malicious files and execute arbitrary code on the server. This affects all versions of ArticleCMS, enabling remote code execution. Any organization using ArticleCMS is vulnerable to complete system compromise.
💻 Affected Systems
- ArticleCMS
📦 What is this software?
Articlecms by Articlecms Project
⚠️ Risk & Real-World Impact
Worst Case
Complete server takeover with persistent backdoor installation, data exfiltration, and lateral movement to other systems in the network.
Likely Case
Webshell deployment leading to data theft, defacement, and use as a pivot point for further attacks.
If Mitigated
Attack blocked at web application firewall level with no file upload functionality accessible to untrusted users.
🎯 Exploit Status
Exploitation is trivial - attackers simply need to upload a malicious file with executable extension. Multiple public PoCs exist.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: None
Vendor Advisory: https://github.com/woider/ArticleCMS/issues/8
Restart Required: No
Instructions:
No official patch exists. Consider migrating to alternative CMS or implementing strict file upload controls.
🔧 Temporary Workarounds
File Upload Restriction
allImplement strict file upload validation including whitelisted extensions, content-type verification, and file size limits.
# Configure in web server or application code
# Example Apache: <Location /upload>
# SetEnvIfNoCase Request_URI "\.(php|phtml|php3|php4|php5|phps|pl|py|jsp|asp|sh|cgi)$" block
# Deny from env=block
# </Location>
Web Application Firewall Rules
allDeploy WAF rules to block malicious file uploads and suspicious POST requests to upload endpoints.
# Example ModSecurity rule:
# SecRule FILES_TMPNAMES "@rx \.(php|phtml|php3|php4|php5|phps|pl|py|jsp|asp|sh|cgi)$" \
# "id:1001,phase:2,deny,status:403,msg:'Blocked malicious file upload'"
🧯 If You Can't Patch
- Disable file upload functionality completely in ArticleCMS configuration
- Isolate ArticleCMS instance in DMZ with strict network segmentation and outbound traffic monitoring
🔍 How to Verify
Check if Vulnerable:
Attempt to upload a file with executable extension (e.g., .php, .jsp) to ArticleCMS upload endpoint. If accepted without validation, system is vulnerable.Check Version:
# Check ArticleCMS version in admin panel or configuration files
# Typically in config.php or similar configuration filesVerify Fix Applied:
Test file upload with executable extensions - should be rejected. Verify WAF logs show blocked attempts.📡 Detection & Monitoring
Log Indicators:
- File uploads with executable extensions
- POST requests to upload.php with suspicious filenames
- Webshell access patterns in access logs
Network Indicators:
- Unusual outbound connections from web server
- POST requests with file uploads to unexpected paths
SIEM Query:
source="web_logs" AND (uri_path="*upload*" OR method="POST") AND (file_extension="php" OR file_extension="jsp" OR file_extension="asp" OR file_extension="py")