What happens if an SSL/TLS certificate expires? Can it be bypassed?

If an SSL/TLS certificate expires, browsers and clients will start issuing warnings about an insecure connection, and some may refuse to establish a connection altogether. This happens because the certificate is no longer considered trusted.

This can be bypassed, but it is not recommended and unsafe. For example:

• In browsers, you can manually add a security exception, but this is only suitable for testing.
• In some clients, you can disable certificate verification (for example, in curl with the -k or --insecure option), but this introduces vulnerabilities.

The correct approach is to update the certificate with the certification authority or use automated solutions, such as Let's Encrypt, for regular renewal.