MSFT.guy released PwnageTool Bundle for iOS 4.2 Beta on iPhone 3GS.With this bundle you can jailbreak your iPhone 3GS on iOS 4.2.If you want to jailbreak your iPhone 3GS with this tool,follow the complete guideline posted below.
The bundles included in this release are not official because they were not issued by the DevTeam.You must be on already pwned 4.1 / 4.0 / lower.iPhone 3GS Old Bootrom and Mac OS only.This is for advanced users only if you don’t know, what you are doing stay away and wait for official Dev team / Geohot tools.Perform the following instructions at your own risk only.
Step 1: Download the iPhone 3GS iOS 4 GM Bundle mentioned in the requirements and unzip to your desktop or where ever you want .
Step 2: Right-click the Mouse on PwnageTool and click on “Show Package Contents”.
Step 3: Then enter “Contents” then “Resources” and finally “FirmwareBundles”.
Step 4: Move the iPhone2,1_4.0_8A293_bundle.zip to the FirmwareBundles folder and close the folder.
Step 5: Launch PwnageTool (now supported for iOS 4.2 Beta ) and proceed normally with the construction of custom firmware.