https://devzone.nordicsemi.com/f/nordic-q-a/128536/server-certificate-expiry-time-is-not-verifiedDear support, We are connecting with an MQTT server with an expired server certificate. My expectation is that the handshake fails, but apparently the NRF9161 accepts the server. I make use of the Nordic SDK v3.3.1, modem firmware 2.0.2, MQTT helperen-USTelligent Community 13Wed, 24 Jun 2026 14:24:17 GMThttps://devzone.nordicsemi.com/thread/568380?ContentTypeID=1Wed, 24 Jun 2026 14:24:17 GMT137ad170-7792-4731-bb38-c0d22fbe4515:0ed3a04f-3f93-4c29-85a0-0ff1315167a2Benjamin<p>Hi Joost,</p> <p>The certificate expiry time is not verified during the TLS handshake, because the modem firmware cannot be guaranteed to have a valid calendar time. Time may be obtained from the network, but this is not guaranteed.</p> <p>Without a valid time, it&#39;s possible that no TLS connection can be opened. To minimize that risk, certificate expiry is not validated. If this validation is a requirement for you, one solution is to move the TLS stack to the application core using Mbed TLS.<br /><br />Best regards,<br />Benjamin</p><div style="clear:both;"></div>