Apple has just released iOS 4.2.1 GM build to developers and luckily enough, iOS 4.2.1 is vulnerable to Redsn0w 0.9.6 b2 released by iPhone dev team. You can go ahead and jailbreak your iPhone 3G, iPhone 3GS, iPhone 4, iPod Touch 2G, iPod Touch 3G, iPod Touch 4G and iPad on iOS 4.2.1.
- if you use Ultrasn0w to unlock your phone, should stay away from this update. There’s no unlock available at this time for iOS 4.2.1
- Golden Master version is targeted for developers, and buggy. Not recomended for end users. Still power users can try.
Jailbreaking iOS 4.2.1
- Open RedSn0w 0.9.6b2, click on “select” & browse for iOS 4.1. When the firmware is identified, it will start execution.
- DONT select “Install Cydia” and then click Next.
- Select the tweaks you wish to have and hit next. Redsn0w will patch and install some files to your iDevice.
- Follow the onscreen instructions to put your iDevice in DFU mode when prompted and your device will be properly jailbreak in seconds.