Chronic Dev Team has just released the Windows version of greenp0ison RC5 that brings untethered jailbreak for all iOS devices running iOS 4.2.1. Here is the step by step guide to jailbreak with greenp0ison RC5.

Before you go for the guide you must know:

- This jailbreak is for all iOS devices running iOS 4.2.1.

- I will not be responsible for any loss of your device while attempting this jailbreak, do it on your own risk.

- This will not unlock your iPhone. If you rely on factory unlock then don’t update to iOS 4.2.1 as it will also upgrade your baseband that is unlockable (so far).

Update: Follow our guide to update iPhone 4 to iOS 4.2.1 without upgrading the 1.59.00 baseband to upgrade to  iOS 4.2.1 without loosing the ability to unlock.

- If your iOS device is already jailbroken on redsn0w 0.9.x running tethered iOS 4.2.1, you can run greenpois0n again to make it untethered.

How to jailbreak:

1. Update your iOS device to iOS 4.2.1.
2. Download greenp0ison from here.
3. Run greenp0ison and connect your iOS device to computer via USB.

   

4. Click “prepare to jailbreak” when you are ready…and follow the instructions on the screen to enter DFU mode.

   

5. If you enter DFU successfully, greenp0ison will start jailbreaking your iOS device to untethered iOS 4.2.1.
6. After the jailbreak is done, run the “Loader” app on the jailbroken iOS device To install Cyda.