CVE-2020-23691
📋 TL;DR
YFCMF v2.3.1 contains a remote command execution vulnerability in index.php that allows attackers to execute arbitrary commands on the server. This affects all systems running this specific version of YFCMF content management system. Attackers can gain complete control of vulnerable systems.
💻 Affected Systems
- YFCMF (Yii Framework Content Management Framework)
📦 What is this software?
Yfcmf by Yfcmf
⚠️ Risk & Real-World Impact
Worst Case
Full system compromise leading to data theft, ransomware deployment, lateral movement within network, and persistent backdoor installation.
Likely Case
Web server compromise leading to website defacement, data exfiltration, and cryptocurrency mining malware installation.
If Mitigated
Limited impact due to network segmentation, minimal privileges, and proper monitoring catching exploitation attempts.
🎯 Exploit Status
The vulnerability is in index.php and appears to be easily exploitable based on GitHub issue discussion. No authentication required.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Unknown
Vendor Advisory: No official vendor advisory found
Restart Required: No
Instructions:
1. Check if running YFCMF v2.3.1
2. Consider upgrading to latest version if available
3. If no patch exists, implement workarounds or replace with alternative CMS
🔧 Temporary Workarounds
Remove vulnerable index.php
linuxTemporarily disable or remove the vulnerable index.php file
mv /path/to/yfcmf/index.php /path/to/yfcmf/index.php.backup
Web Application Firewall rules
allImplement WAF rules to block RCE attempts
🧯 If You Can't Patch
- Isolate the system in a DMZ with strict network segmentation
- Implement strict file integrity monitoring on index.php and related files
🔍 How to Verify
Check if Vulnerable:
Check YFCMF version in configuration files or admin panel. Look for version 2.3.1.Check Version:
grep -r 'version.*2.3.1' /path/to/yfcmf/ || find /path/to/yfcmf -name '*.php' -exec grep -l '2.3.1' {} \;Verify Fix Applied:
Verify index.php has been modified or removed. Test with controlled RCE attempts if safe environment.📡 Detection & Monitoring
Log Indicators:
- Unusual POST requests to index.php with command execution patterns
- System commands executed from web server process
- Web server error logs showing command execution attempts
Network Indicators:
- HTTP requests with command injection payloads to index.php
- Outbound connections from web server to suspicious IPs
SIEM Query:
source="web_logs" AND uri="/index.php" AND (request_body CONTAINS "system(" OR request_body CONTAINS "exec(" OR request_body CONTAINS "shell_exec(")