CVE-2021-3172
📋 TL;DR
This vulnerability in PHP-Fusion allows authenticated attackers to cause a Distributed Denial of Service (DDoS) via the polling feature. Attackers with valid user accounts can exploit this to overwhelm server resources. Only PHP-Fusion installations running vulnerable versions are affected.
💻 Affected Systems
- PHP-Fusion
📦 What is this software?
Php Fusion by Php Fusion
⚠️ Risk & Real-World Impact
Worst Case
Complete service unavailability due to resource exhaustion, potentially affecting all users of the PHP-Fusion application.
Likely Case
Degraded performance or temporary service disruption for legitimate users.
If Mitigated
Minimal impact with proper rate limiting and monitoring in place.
🎯 Exploit Status
Exploitation requires authenticated access but is technically simple once access is obtained
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: v9.10.00
Vendor Advisory: https://github.com/PHPFusion/PHPFusion/commit/7b8df6925cc7cfd8585d4f34d9120ff3a2e5753e
Restart Required: No
Instructions:
1. Backup your current PHP-Fusion installation and database. 2. Download PHP-Fusion v9.10.00 or later from the official repository. 3. Replace vulnerable files with patched versions. 4. Verify the installation works correctly.
🔧 Temporary Workarounds
Disable Polling Feature
allTemporarily disable the polling feature to prevent exploitation
Edit PHP-Fusion configuration to disable polling functionality
Implement Rate Limiting
allAdd rate limiting to polling requests to prevent abuse
Configure web server or application rate limiting for polling endpoints
🧯 If You Can't Patch
- Restrict user account creation and implement strong authentication controls
- Implement network-level rate limiting and monitor for unusual polling activity
🔍 How to Verify
Check if Vulnerable:
Check PHP-Fusion version in admin panel or by examining version filesCheck Version:
Check includes/core_functions_include.php or admin panel version displayVerify Fix Applied:
Verify version is v9.10.00 or later and test polling functionality📡 Detection & Monitoring
Log Indicators:
- Unusually high frequency of polling requests from single users
- Resource exhaustion alerts (CPU/memory spikes)
Network Indicators:
- High volume of requests to polling endpoints
- Abnormal traffic patterns from authenticated sessions
SIEM Query:
source="php-fusion-logs" AND (uri="*/polling*" OR uri="*/vote*") AND count > threshold