iPhone Dev Team has released a new version of Redsn0w to jailbreak iOS 4.2.1 for iPhone 4, iPhone 3GS, iPhone 3G, iPod Touch 4G, iPod Touch 3G, iPad and Apple TV 2G.

Redsn0w 0.9.6b4 makes use of Geohot’s USB bootrom exploit used in limera1n for iOS 4.1.

Redsn0w 0.9.6b4 is available for both Mac and Windows users.

As Dev team had explained in the update yesterday there is good news if you are an iPhone 3G, older iPhone 3GS, and non-MC iPod touch 2G user and some bad news for users who own an iPhone 3GS (new bootrom), iPhone 4, iPad, iPod touch 2G (MC Model), iPod touch 3G and the iPod touch 4G.

iPhone 3G, older iPhone 3GS, and non-MC iPod touch 2G users will be able to enjoy the benefit of an untethered iOS 4.2.1 jailbreak using Redsn0w.

Unfortunately, iPhone 3GS (new bootrom), iPhone 4, iPad, iPod touch 2G (MC Model), iPod touch 3G and the iPod touch 4G users will have to manage with a tethered iOS 4.2.1 jailbreak using Redsn0w. As Dev team had explained yesterday:

A tethered jailbreak means that each time your device loses battery power or needs to be rebooted, you must attach it to a PC or Mac to boot into the jailbroken state.

Comex is working hard to bring a untethered iOS 4.2.1 jailbreak for users with newer devices so we’ll let you know if we have any further updates.

Redsn0w will NOT hactivate or unlock your iPhone. So if you want to unlock your iPhone and currently have iOS 4.1 or lower running on your iPhone then please wait for Dev team to release PwnageTool for iOS 4.2.1 as it preserves the baseband from getting upgraded so that you can use Ultrasn0w to software unlock your iPhone. Dev team is also expected to release a new version of Ultrasn0w shortly for iPhone 3GS and iPhone 3G users. They have mentioned that the unlock for iPhone 4 users will need more effort and are not in a position to provide any further information currently.

Please remember that jailbreaking your iPhone may void its warranty so proceed with caution.

You can download Redsn0w using the download link provided by Dev team at the bottom of their post.

Please don’t forget to let us know how it goes.