Apple released iOS 4.2.1 back in December 2010. Since then iPhone dev-team and various hackers started working on a jailbreak for iPhone, iPad and iPod Touch models. Now on today Chronic dev team released a simple iOS 4.2 jailbreak tool for all supported idevices. The advantage of GreenPois0n RC5 is that it’s an untethered jailbreak tool, and it supports multiple OS platforms. Mac OS version is currently available for download and soon Windows and Linux users would be able to download native versions of GreenPois0n RC5 for their platforms.
Right now we have tethered and untethered jailbreak tools available for iOS 4.2.1 supported devices. The tethered solution Redsn0w 0.9.6 b4 is pretty much easy to implement, but you will need to connect your device to a Mac or PC to restart it into the jailbreak mode. The untethered jailbreak tools in Redsn0w 0.9.7 series are still under testing and for which you need your iOS 4. 2b3 Signature Hash files saved on Cydia server. GreenPois0n RC5 jailbreak doesn’t need iOS ipsw files or SHSH backup so it seems to be the most convenient method available at this point.
Download GreenPois0n RC5
Download GreenPois0n RC5 for Mac (here).
Updated: New version of GreenPois0n, Greenpois0n RC5_2 is now available for download. A few bugs in the first version, especially the freezing problem after greenpois0n initialization is now fixed.
Download GreenPois0n RC5 Windows (here), Linux (here).
Update: Download Greenpois0n Rc6.1 here. (iBooks issue with jailbroken devices has been fixed)
There is some issue with GreenPois0n RC5 for Linux download link. We will update the link as soon as the software is made public. Here is our detailed step by step guide to jailbreak iOS 4.2.1 on Windows and Mac using GreenPois0n RC5.