GreenP0ison RC5_2 has now enabled the iPhone users to jailbreak iPhone 4.2.1 firmware untethered for all iOS devices.
GreenPoison RC5_2 don’t require you to have saved SHSH blobs of previous versions of iOS on Cydia.
The IOS 4.2.1 untethered Jailbreak using Greenp0ison works with any iOS device out of the box.
To untethered jailbreak 4.2.1 iOS for iPhone 3GS, iPhone 4, iPod touch 2G/3G/4G, iPad and Apple TV 2G, follow these steps:
(Please note: if you rely on unlocking your device to use your current cellular network carrier, then don’t update to 4.2.1 yet)
Step 1: Download GreenP0ison (link not working: http://www.greenpois0n.com/ ) (for windows or Mac OSX) and run
Step 2: Connect your iPhone to computer anc click on “Jailbreak” to begin the process to jailbreak iPhone 4.2.1 firmware.
Step 3: Follow the on screen instructions to enter the DFU mode
Step 4: Your device with iOS 4.2.1 will now be Jailbrokon by the GreenP0ison untethered.
Step 5: Done. Your Apple device (iPhone, iPod touch or iPad on iOS 4.2.1 ) is now jailbroken untethered. Start the loader on the homescreen to install Cydia and it’s all complete!
Your iPhone, iPad or iPod touch should now be successfully jailbroken on iOS 4.2.1. Now start “Loader” found on the homescreen and install Cydia.
This is it! You are done !
Download iOS 4.2.1 for iPhone 4, 3GS, iPod touch 4G / 3G / 2G and iPad