Definition - What does VPN Firewall mean?
A VPN firewall is a type of firewall device that is designed specifically to protect against unauthorized and malicious users intercepting or exploiting a VPN connection.
It can be in the form of hardware, software or an all-in-one firewall appliance, with the core objective to allow only legitimate VPN traffic access to the VPN.
Techopedia explains VPN Firewall
A VPN firewall is typically installed at the server end of a VPN, either at the front or back of the VPN server. When the firewall is installed at the back of a VPN server, it is configured with filters to allow only VPN-specific packets to pass. Similarly, when the firewall is installed at the front of a VPN, the firewall is configured to allow only tunnel data on its Internet interface to be passed to the server.