Attack Chain

1. Attacker identifies a vulnerable FreePBX instance with an exposed UCP interface.
2. Attacker accesses the UCP interface without authentication.
3. Attacker leverages the hard-coded credentials present in the vulnerable Security-Reporting userman module.
4. Attacker gains unauthorized access to user accounts and system settings.
5. Attacker modifies user permissions or creates new administrative accounts.
6. Attacker uses the elevated privileges to access sensitive call records and configuration files.
7. Attacker may install malicious modules to further compromise the system.
8. Attacker achieves full system compromise, potentially leading to eavesdropping on calls, denial-of-service, or further lateral movement within the network.

Impact

Successful exploitation of this vulnerability could lead to complete compromise of the FreePBX system. This includes unauthorized access to call records, modification of system configuration, and the potential for eavesdropping on phone calls. Organizations relying on FreePBX for their telecommunications infrastructure are at risk of data breaches, service disruptions, and financial losses. Given the widespread use of FreePBX, a large number of organizations could be affected by this vulnerability.

Recommendation

• Immediately upgrade FreePBX Security-Reporting userman module to versions later than 16.0.45 (FreePBX 16) and 17.0.7 (FreePBX 17) to remediate the hard-coded credentials vulnerability.
• Monitor access logs for suspicious activity related to the UCP interface, looking for unauthenticated access attempts (reference: overview).
• Implement network segmentation to limit the exposure of the FreePBX system and UCP interface to internal networks only.