The latest iOS 4.2.1 Jailbreak GreenPois0n RC5 have been released on February recently by Chronic Dev Team which bring full untethered for all iOS devices. It does not required to have SHS blobs to be save on Cydia and you can jailbreak the device out from the box which running on iOS 4.2.1 with this latest GreenPois0n RC5.

The following instruction will guide you on how to jailbreak iOS 4.2.1 on iPhone 4, 3GS, iPod touch 2G/3G/4G, iPad and Apple TV 2G.

NOTE : If your IPhone 4 required to unlock, do not use this patch as doing so will upgrade your baseband, making it impossible to unlock.

Step 1 : Download GreenPois0n for Windows or MAC

NOTE : Make sure to backup your devices using iTunes and make sure the devices is running on iOS 4.2.1 before proceed on the following steps.

Step 2 : Power off your devices

Step 3 : Connect your device via USB to the computer and run the GreenPois0n program

Step 4 : Press the “Jailbreak” button and follow the onscreen instructions to enter DFU mode

• Press and hold the sleep button for 2 seconds
• Continue holding sleep; press and hold home for 10 seconds.
• Release sleep button; continue holding home for 15 seconds.

Step 5 : The application will start to jailbreaking on your iOS device and will reboot the device

Step 6 : You’re almost done, on the homescreen will appear “Loader” and start the “Loader” to install the Cydia, make sure to install the SSH from Cydia. Then change the root password of your device to protect from any unauthorized access from public since the default root password is “alpine”.