Transport Layer Security, or TLS, is the encryption protocol that secures many network connections, including HTTPS. It protects data in transit from being read or changed by anyone on the network path, and it lets a client confirm it is talking to the intended server. To do this, the client checks the server's certificate, including whether it was issued by a trusted authority and whether it matches the hostname being contacted.
That hostname check is what stops an attacker from presenting a valid certificate for a different site and impersonating the server. Software that skips or weakens certificate verification, or that contains a bug in how it matches names, can accept connections it should reject. For that reason, a TLS bug can matter even when the encryption itself is working.
TLS protects the connection, not the application on the other end. A properly encrypted connection can still carry a malicious request to a vulnerable server, and a valid certificate does not show that the server is safe or patched. Likewise, a connection that uses TLS is not proof that every check in the client or library worked as intended.
To keep TLS effective, run supported versions of your runtime and TLS libraries, apply vendor updates that touch certificate handling, do not disable certificate verification in production code, and monitor certificate expiry. After patching, confirm the running version and test that connections to a host with the wrong certificate are refused.