Network misconfigurations

Elastic Load Balancer (ELB) allows ingress access to Oracle DB port 1521


Oracle TNS (Transparent Network Substrate) port - 1521 is used by Oracle client to connect to the database server over Oracle SQL Net protocol. Allowing inbound traffic from all external IP addresses on TNS port will let commands to be sent to the listener - the listener can be shut down, or the databases can be queried. It is a best practice to block public access and restrict access from specific IP addresses to port 1521.