Apple yesterday released the iOS 4.2.1 update for its line of touch screen devices, and hackers wasted no time in getting the jailbreak software released to the internet community.
The iPhone Dev-Team have released a new version of redsn0w for both Mac OS X and Windows that will jailbreak all iOS 4.2.1 compatible devices. Depending on which device, however, it could result in a 'tethered' jailbreak. This means that anytime the device loses power or gets rebooted, it will have to be reconnected to a computer again before returning to the jailbreak state.
The exception to this is old devices such as the iPhone 3G, iPhone 3GS models with older bootrom version, and non-MC iPod touch 2G. These devices are still vulnerable to older exploits and will still retain their jailbreak even after a power cycle.
Those who rely on a carrier unlock should steer clear of this jailbreaking solution for now, as there is no way of retaining the unlocked state through the redsn0w software.
Read more at the Dev-Team blog.