The good point is that because of this (and the fact that Apple fixed the kernel exploit in 4.3), we’re all working back on releasing gp.So GreenPois0n RC5 will be released very soon for iOS 4.2.1 on all devices. Stay tuned for more updates as they come ! [Source: Twitter]
GreenPois0n untethered jailbreak won't work on iOS 4.3
It looks like GreenPois0n untethered jailbreak will be available very soon as announced by iPhone hacker pod2g, Apple has closed the loophole hackers have been using up until iOS 4.3.