CVE-2022-28055
📋 TL;DR
CVE-2022-28055 is a command injection vulnerability in FusionPBX's email log download function that allows authenticated attackers to execute arbitrary commands on the server. This affects all FusionPBX installations version 4.4 and below. Attackers with administrative access can exploit this to gain full control of the affected system.
💻 Affected Systems
- FusionPBX
📦 What is this software?
Fusionpbx by Fusionpbx
⚠️ Risk & Real-World Impact
Worst Case
Complete system compromise allowing attackers to execute arbitrary commands as the web server user, potentially leading to data theft, lateral movement, or installation of persistent backdoors.
Likely Case
Authenticated attackers with administrative privileges can execute arbitrary commands to compromise the server, access sensitive data, or disrupt services.
If Mitigated
With proper access controls and network segmentation, impact is limited to the affected application server, though command execution would still be possible.
🎯 Exploit Status
Exploitation requires administrative credentials. The vulnerability is in the download.php file where user input is passed to system() calls without proper sanitization.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: v4.5 and above
Vendor Advisory: https://github.com/fusionpbx/fusionpbx/commit/4e260b170e17705c4c9ccf787be7711b63a40868
Restart Required: No
Instructions:
1. Backup your current installation. 2. Update to FusionPBX v4.5 or later. 3. Apply the specific patch from the GitHub commit if not updating fully. 4. Verify the fix by checking that the vulnerable code in download.php has been patched.
🔧 Temporary Workarounds
Disable vulnerable function
linuxRemove or restrict access to the email log download functionality
# Remove or rename the vulnerable file
mv /var/www/fusionpbx/app/email_logs/download.php /var/www/fusionpbx/app/email_logs/download.php.disabled
Implement input validation
allAdd input sanitization to the download.php file
# Add input validation before system() calls
# Example: escape shell arguments using escapeshellarg()
🧯 If You Can't Patch
- Restrict administrative access to only trusted users and implement strong authentication
- Implement network segmentation to isolate the FusionPBX server from critical systems
🔍 How to Verify
Check if Vulnerable:
Check if running FusionPBX v4.4 or below and examine the download.php file for unsanitized system() calls with user input.Check Version:
grep 'software_version' /var/www/fusionpbx/resources/config.php | grep -o '[0-9]\+\.[0-9]\+'Verify Fix Applied:
Verify the system is running v4.5 or above, or check that the download.php file includes proper input sanitization using escapeshellarg() or similar functions.📡 Detection & Monitoring
Log Indicators:
- Unusual commands in web server logs related to email log downloads
- Suspicious system commands executed by the web server user
Network Indicators:
- Unusual outbound connections from the FusionPBX server
- Command and control traffic patterns
SIEM Query:
source="fusionpbx_logs" AND ("download.php" OR "email_logs") AND command="*"