CVE-2021-41739
📋 TL;DR
This CVE describes an OS command injection vulnerability in Artica Proxy's cyrus.events.php file. Attackers can execute arbitrary operating system commands by manipulating GET and POST parameters, potentially leading to full system compromise. Organizations running Artica Proxy 4.30.000000 are affected.
💻 Affected Systems
- Artica Proxy
📦 What is this software?
Artica Proxy by Articatech
⚠️ Risk & Real-World Impact
Worst Case
Full system compromise allowing attackers to execute arbitrary commands as the web server user, potentially leading to data theft, lateral movement, ransomware deployment, or complete system takeover.
Likely Case
Remote code execution leading to web shell installation, credential harvesting, and establishment of persistent backdoors for further attacks.
If Mitigated
Limited impact if proper network segmentation, least privilege principles, and input validation are implemented, though the vulnerability still presents significant risk.
🎯 Exploit Status
Exploitation is straightforward with publicly available proof-of-concept code. Attackers can execute commands without authentication by manipulating HTTP parameters.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Update to version 4.50 or later
Vendor Advisory: https://artica-proxy.com/
Restart Required: Yes
Instructions:
1. Backup current configuration and data. 2. Download the latest version from the official Artica Proxy website. 3. Follow the vendor's upgrade instructions. 4. Restart the Artica Proxy service. 5. Verify the update was successful.
🔧 Temporary Workarounds
Input Validation and Sanitization
allImplement strict input validation for the 'logs' GET parameter and 'rp' POST parameter in cyrus.events.php
Modify cyrus.events.php to validate and sanitize user inputs before processing
Web Application Firewall Rules
allDeploy WAF rules to block malicious patterns in HTTP requests targeting cyrus.events.php
Add WAF rules to detect and block command injection patterns in GET and POST parameters
🧯 If You Can't Patch
- Implement strict network segmentation to isolate Artica Proxy from critical systems
- Deploy application-level controls to monitor and block suspicious command execution attempts
🔍 How to Verify
Check if Vulnerable:
Check if Artica Proxy version is 4.30.000000 and examine cyrus.events.php for lack of input validation on 'logs' and 'rp' parametersCheck Version:
Check the Artica Proxy web interface or configuration files for version informationVerify Fix Applied:
Verify the Artica Proxy version is 4.50 or later and test that command injection attempts are properly blocked📡 Detection & Monitoring
Log Indicators:
- Unusual command execution patterns in system logs
- Suspicious HTTP requests to cyrus.events.php with shell metacharacters
- Unexpected process creation from the web server user
Network Indicators:
- HTTP requests containing shell commands in GET/POST parameters
- Outbound connections from the proxy server to unexpected destinations
SIEM Query:
source="artica-proxy" AND (uri="*cyrus.events.php*" AND (param="*;*" OR param="*|*" OR param="*`*" OR param="*$(*"))