Need to jailbreak 4.2.1? If the answer is yes then GreenPois0n RC5 has just been released by Chroic Dev Team providing an untethered iOS 4.2.1 Jailbreak.
The great advantage of Chronic Dev Team’s GreenPois0n RC5 is that you no longer need SHSH blogs of 4.2b3 in Cydia, and all iOS device can be jailbroken out of the box.
Follow the instruction below to Jailbreak 4.2.1:
1: Download GreenPois0n RC5 from http://www.greenpois0n.com/ (On page select either MAC, PC or Linux)
2. Connect your iPhone, iPad or iPod via USB to your computer and click “Jailbreak” (seen below)
3. Follow the onscreen instructions to enter DFU mode:
4. GreenPois0n will now Jailbreak your iOS device untethered on 4.2.1.
5. 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.