iOS update via iTunes to latest MINOR version?

Normally, if you have difficulties updating OTA, then you can manually fetch the updater, an .ipsw file, & run it manually from iTunes [Finder in newer macOS.]

If you are trying to update to the latest iOS, then iTunes will usually find the correct file for you. If, as in this case, there is a security update for an earlier iOS then you may have to fetch it manually.

ipsw.me contains lists of .ipsw files for all devices, going back into the mists of time. They do not store the content, merely the correct addresses to where Apple keeps these updates.
They are only useful for as long as Apple are still signing the update - usually a couple of weeks after the next update is released; the window of opportunity can be short.

If you download one of these, then in iTunes you Opt ⌥ click the Update button & you will be asked to choose a file to update from, rather than the automatic process. Once chosen, assuming it's the correct file & still being signed, then the update will proceed in the same way as any regular update.