CVE-2021-43464
📋 TL;DR
This vulnerability allows remote attackers to execute arbitrary code on Subrion CMS 4.2.1 systems by injecting malicious code into a background field that gets executed via eval(). All Subrion CMS 4.2.1 installations with the vulnerable component are affected.
💻 Affected Systems
- Subrion CMS
📦 What is this software?
Subrion Cms by Intelliants
⚠️ Risk & Real-World Impact
Worst Case
Complete system compromise allowing attacker to install malware, steal data, pivot to internal networks, or establish persistent backdoor access.
Likely Case
Website defacement, data theft, or installation of cryptocurrency miners or botnet clients.
If Mitigated
Limited impact with proper input validation and output encoding preventing code injection.
🎯 Exploit Status
Exploitation requires ability to modify the vulnerable field, which may require authentication. The eval() vulnerability is straightforward to exploit once access is obtained.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 4.2.2 or later
Vendor Advisory: https://github.com/intelliants/subrion/issues/888
Restart Required: No
Instructions:
1. Backup your Subrion installation and database. 2. Download the latest Subrion version from the official repository. 3. Replace vulnerable files with patched versions. 4. Verify functionality after update.
🔧 Temporary Workarounds
Disable vulnerable component
allRemove or disable the background field functionality that uses eval()
# Locate and modify the vulnerable PHP file to remove eval() usage
Input validation hardening
allImplement strict input validation for the background field
# Add input sanitization before eval() call in the vulnerable file
🧯 If You Can't Patch
- Implement web application firewall (WAF) rules to block eval() and code injection patterns
- Restrict access to the vulnerable interface using network segmentation and authentication controls
🔍 How to Verify
Check if Vulnerable:
Check if running Subrion CMS version 4.2.1 and examine code for eval() usage in background field processing.Check Version:
Check Subrion admin panel or examine includes/version.php fileVerify Fix Applied:
Verify version is 4.2.2 or later and test that malicious code in background field no longer executes.📡 Detection & Monitoring
Log Indicators:
- Unusual eval() calls in PHP logs
- Unexpected background field modifications
- Suspicious POST requests to admin interfaces
Network Indicators:
- HTTP requests containing eval() patterns or PHP code in parameters
- Outbound connections from web server to unknown destinations
SIEM Query:
source="web_logs" AND (eval OR base64_decode OR system OR exec) AND uri="*/admin/*"