If you have been religiously jailbreaking your iPhone over the years, you may have become used to this application called Tiny Umbrella that helps your device kick itself out of the recovery mode during the jailbreak process. This is a nifty application because it helps you to upgrade the device firmware without affecting the baseband.
It now appears that Apple may have introduced, albeit partially, a baseband requirement which means applications such as Tiny Umbrella may no longer be able to get your iPhone out of recovery mode. Semaphore, the developer behind Tiny Umbrella notes,
“It seems that Apple has decided to put a baseband requirement on iOS. So at this point, if you are using Saurik’s server or tiny umbrella and trying to restore 4.2.1 on an iPhone 4, you will end up in recovery mode and tiny umbrella will not be able to pull you out of recovery.”
This is speculated to be partial because other jailbreakers do not seem to have been having a problem themselves. Popular jailbreaker MuscleNerd has written,
“4.2.1 is running fine on my i4 with 01.59 BB. I think they simply killed Umbrella way.”