Jailbreak iOS 4.2.1, Hackers from Chronic Dev have launched a new untethered tool that lets you Jailbreak your iOS 4.2.1 devices. It’s a new version of Greenpois0n, namely Greenpois0n 4.2.1.
With this tool you can reboot your Device without re- jailbreak. According to PC World the jailbreak is available for Mac, Linux, and Windows, just download the zip file from greenpois0n.com to your computer. But some report says that the Jailbreak is available only for Mac.
The Greenpois0n.com is now down may be with rush to download it, you may have to wait for a few minutes browsing the site.
When you try to do it, don’t forget to back up your data and you yourself bear all the risk it could bring to your device. feel free to command on the tool.