iPhone Dev Team has released PwnageTool 4.1.2 to jailbreak iOS 4.1. One of the major advantage of PwnageTool 4.1.2 jailbreak tool is that it let you create custom firmware which you can use to jailbreak iPhone 4, iPhone 3GS, iPhone 3G on iOS 4.1. You can alternatively build iOS 4.1 custom firmware if you do not get successful in creating one.
Download iOS 4.1 Custom Firmware
Step 1: Download the following iOS 4.1 custom firmwares
Download custom firmware for iPhone 4 on iOS 4.1
Download custom firmware for iPhone 3GS on iOS 4.1
Download custom firmware for iPhone 3 on iOS 4.1
Step 2: Join all the parts of respective firmware for your iOS devices using HJSplitter or BetterZip
Step 3: Start iTunes 10 and put your iPhone into DFU mode
Step 4: Once your iPhone is in DFU mode click on iPhone icon and quickly hold left ‘Alt’ button and click on ‘Restore’ option on left side. Now release ‘Alt’ button. It will automatically restore your iOS 4.1 custom firmware on iPhone.
That’s it! You’ve successfully installed iOS 4.1 custom firmware on iPhone. This will also jailbreak your device. Use ultrasn0w to unlock your iOS devices.