iOS 11.3 (build 15E216) is an official Apple over-the-air update for the iPhone SE, released on 2018-03-29T17:13:14Z. The update package is 667.07 MB. This is a delta (partial) update that requires 11.2.5 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 48dc538d97eca7c85fff47a6e73d0bc4155a6d9f.zip.