Jailbreak 4.2.1 with redsn0w 0.9.6b4
MartiniBoy got out in front with this
earlier today, but I just wanted to make sure the news was on the main page. The Dev-Team updated redsn0w to version 0.9.6b4
today, which, as Nick detailed yesterday
, provides an untethered jailbreak of iOS 4.2.1 for iPhone 3G, older iPhone 3GS, and non-MC iPod touch 2G, and a tethered JB for the iPhone 3GS (new bootrom), iPhone 4, iPad, iPod touch 2G (MC model), iPod touch 3G and the iPod touch 4G. thanks to a combination of pwnage2 exploit, the arm7_go exploit, 24kpwn, and limera1n. For best results, upgrade to iTunes 10.1 first.
Again, it's very important
to note that if you unlock, you cannot
use redsn0w as it will update your baseband. So if you're an unlocker, or have a newer iDevice and would just prefer the security of an untethered JB, wait for the PwnageTool update before loading 4.2.1. Even if you are ready (like I was) to take the plunge, make sure you back up your SHSH first.
Source: Dev-Team Blog