iOS 11.2.1 (build 15C153) is an official Apple over-the-air update for the iPhone SE, released on 2017-12-13T18:14:07Z. The update package is 1.09 GB. This is a delta (partial) update that requires 10.2 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 35efe218ab55ecdd9fbf231db1a59a6142f59df9.zip.