iOS 11.3.1 (build 15E302) is an official Apple over-the-air update for the iPhone SE, released on 2018-04-24T17:11:11Z. The update package is 1.31 GB. This is a delta (partial) update that requires 10.3.3 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 3f21a6ce4030fe484fe83e9a0b9f3049aac17f55.zip.