CVE-2021-40889
📋 TL;DR
CMSUno 1.7.2 contains a PHP code execution vulnerability that allows attackers to inject malicious PHP code into the password.php file. This enables remote code execution on affected web servers. Any organization running vulnerable CMSUno versions is at risk.
💻 Affected Systems
- CMSUno
📦 What is this software?
Cmsuno by Cmsuno Project
⚠️ Risk & Real-World Impact
Worst Case
Complete server compromise allowing attackers to execute arbitrary commands, steal data, install backdoors, or pivot to other systems.
Likely Case
Webshell deployment leading to data theft, defacement, or use as part of a botnet.
If Mitigated
Limited impact if proper input validation and file permission controls are implemented.
🎯 Exploit Status
The vulnerability is well-documented in public GitHub issues with technical details that could be weaponized.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Versions after 1.7.2
Vendor Advisory: https://github.com/boiteasite/cmsuno/issues/19
Restart Required: No
Instructions:
1. Upgrade CMSUno to the latest version. 2. Replace the vulnerable uno/central.php file with the patched version. 3. Remove any existing password.php files that may contain malicious code.
🔧 Temporary Workarounds
Restrict file permissions
linuxSet strict file permissions on password.php to prevent writing
chmod 444 /path/to/uno/password.php
Input validation filter
allAdd input validation to prevent PHP code injection
🧯 If You Can't Patch
- Implement WAF rules to block suspicious PHP code patterns in POST requests
- Monitor and restrict access to the uno/central.php endpoint
🔍 How to Verify
Check if Vulnerable:
Check if CMSUno version is 1.7.2 by examining the version file or checking the uno/central.php file for the vulnerable sauvePass action.Check Version:
cat /path/to/cmsuno/version.txtVerify Fix Applied:
Verify the version is updated beyond 1.7.2 and check that password.php file contains only expected username data, not executable PHP code.📡 Detection & Monitoring
Log Indicators:
- Unusual POST requests to uno/central.php with sauvePass parameter
- File modifications to password.php with PHP code patterns
Network Indicators:
- HTTP requests containing PHP code snippets in POST data
- Traffic to uno/central.php with suspicious payloads
SIEM Query:
source="web_logs" AND uri="/uno/central.php" AND method="POST" AND (data CONTAINS "<?php" OR data CONTAINS "eval(" OR data CONTAINS "system(")