iOS 11.2.1 (build 15C153) is an official Apple over-the-air update for the iPhone SE, released on 2017-12-13T18:14:20Z. The update package is 316.15 MB. This is a delta (partial) update that requires 11.1 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 50afe5a5bbbe42b3553efcff3c1d2a76fa393dcb.zip.