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 1.27 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: 499611958ea667fd84f83959c716041831bd33d1.zip.