If two hosts (Host1 and Host2) successfully accomplish a TCP handshake process and have a connection, would a third host (Host3) be able to send messages directly to Host1's address and (ephemeral) port once it knows them, spoofing these messages with Host2's address and port?
In other words:
Host1 (192.0.2.115:32154) <-------------> (198.51.100.10:7184) Host2
Host3 sends a message directly to 192.0.2.115:32154, spoofing it's source port and address to 198.51.100.10:7184.
Would this work, or does TCP have some mechanism that avoids it? As TCP sessions are identified by source and destination addresses and ports and they would have been spoofed, I can't see how can this message be known as being bogon.