Devteam’s MuscleNerd updated on Twitter that Jailbreak for iPhone OS 4.0 beta 1 is out for public. Since this is a beta release of redsn0w (v 0.9.5 BETA) Normal users should stay away from it. Generally it is meant for developers of jailbroken apps to fix their apps before the general public gets iOS 4.0. They used the same pwnage2 DFU-mode exploit that they’ve been using since the 2.x days but it’s not applicable to the iPad.
iPhone users who use blacksn0w, yellowsn0w or ultrasn0w should stay away from it if you dont want to unlock your phone. That’s because the beta redsn0w works only if your device has already been upgraded to the stock 4.0beta1 IPSW from Apple, which contains a baseband update. If you installed that IPSW, you’ve already lost the carrier unlock until the next planned release of ultrasn0w and blacksn0w.
For more information as well as directions on how to use the beta RedSn0w 0.9.5 to jailbreak the iPhone 4.0 beta 1, check out the Dev Team wiki.
Note that this jailbreak is for iPhone OS 4 beta 1 only. It will not jailbreak or unlock any other firmware.This BETA release supports on iPhone 3G and only a MAC OSX version of redsn0w is available now. You can download the redsn0w (v 0.9.5 BETA) from here (Official link)