Apple has posted iOS 14.2.1. You can obtain it by going to Settings > General > Software Update on your iPhone.
Note that the upgrade is only available for the iPhone 12 line-up. Here are Apple’s release notes:
iOS 14.2.1 addresses the following issues for your iPhone:
– Some MMS messages may not be received
– Made for iPhone hearing devices could have sound quality issues when listening to audio from iPhone
– Lock Screen could become unresponsive on iPhone 12 mini