Apple has ceased signing baseband firmware for a selection of older iPhone and iPad models, effectively preventing users from restoring or downgrading to specific iOS versions on these devices. This action specifically targets the low-level software managing the cellular modem, not the main iOS builds.

The affected devices include cellular variants of the iPhone 4 (CDMA), iPhone 4S, iPhone 5, iPhone 5c, iPad 2, iPad 3rd generation, iPad 4th generation, and iPad mini. For example, iPhone 5c models can no longer restore to iOS 10.3.3, and iPhone 5 devices lose the ability to restore to iOS 10.3.4.

This move removes a fallback option for users who wanted to reinstall older operating systems on their aging hardware, whether for app testing or preserving specific software states. While devices already running the affected firmware will continue to function normally, the ability to perform a fresh install of these particular builds is now gone. This is an unusual step, as Apple typically stops signing firmware for much more recent releases, often tied to security updates.