DevTeam worked hard for the last several hours and released jailbreak tool for iOS 4.2.1. It is redsn0w 0.9.6 b4.
As usual we remind all ultrasn0w unlockers please stay away from this official firmware. Wait for the ability to create custom 4.2.1 IPSWs that don’t update your baseband!
New redsn0w 0.9.6 b4 uses limera1n exploit and will successfully jailbreak all devices. The only problem is that it is a tethered jailbreak, which means you will have to plug it to a computer and rerun redsn0w on every reboot. This so called tethered or semi-tethered jailbreak. This condition applies to iPhone 3GS (new bootrom), , iPad, iPod touch 2G (MC model), iPod touch 3G and iPod touch 4G. Hackers are working hard to create untethered jailbreak for these devices. To use future untethered jailbreak you need to save SHSH keys for iOS 4.1 using utility or directly in Cydia.
Old devices like iPhone 3GS (old bootrom), iPhone 3G and iPod touch 2G (non-MC model) can be jailbroken-untethered right now using this latest version of RedSn0w.
You cannot use JailBreakMe method to jailbreak and unlock iOS 4.0.2 on iPhone 3G. However you can still jailbreak and unlock iPhone 3G using redsn0w. Here are the instructions:
Run RedSn0w and point it at the 4.0 IPSW. (Yes – point it at the 4.0 IPSW even though you’re at 4.0.2). This will also hacktivate your iPhone3G at 4.0.1 if you haven’t already been activated by iTunes.
If you need a carrier unlock – install ultrasn0w in Cydia (add repository http://repo666.ultrasn0w.com). For T-Mobile in the USA remember to turn off 3G mode in Settings→General→Network.
Run RedSn0w and point it at the 4.0 IPSW. (Yes – point it at the 4.0 IPSW even though you’re at 4.0.1). This will also hacktivate your iPhone3G at 4.0.1 if you haven’t already been activated by iTunes.
Install ultrasn0w in Cydia (add repository http://repo666.ultrasn0w.com) if you need a carrier unlock (and in the USA, remember to turn off 3G mode in Settings→General→Network).
DevTeam updated iOS 4 jailbreak utility redsn0w to version 0.9.5b5-5. That should fix any APN or MMS issues that users were seeing. It’s safe to re-run it on an already jailbroken iPhone without restoring. Just deselect “Install Cydia” if you do that.
Supported devices are still only iPhone3G and iPod Touch 2G (not MC)
DevTeam successfully jailbreaked new iOS 4. They updated jailbreak utility redsn0w to version 0.9.5b5-3. Supported devices are iPhone3G and iPod Touch 2G (not MC). New redsn0w is also able to hacktivate iOS 4.0 for iPhone3G.
