Now that Apple has released iOS 4.2.1, many of you will be eager to jailbreak iPad 4.2.1. So, here is a step-by-step guide to help you jailbreak iOS 4.2.1 on iPad (3G / wi-fi) using Pwnagetool 4.2.1 modified version created by Nadeem Ateyeh which has working Cydia and hence no need to go through complex steps of compiling & patching Cydia manually.
Important: This is a tethered jailbreak, meaning every time you reboot your iPad you have to re-jailbreak by following below method. Moreover this is the modified version of PwntageTool and not widely tested. So, go for it only if you understand the risks involved.
[How to] Jailbreak iPad iOS 4.2.1 with PwnageTool 4.2.1
2. Download Modified PwnageTool 4.2.1 (Unofficial & not supported by iPhone Dev team)
3. Start PwnageTool 4.2.1 and create iPad iOS 4.2.1 custom firmware
4. Connect iPad to PC & put your iPad in DFU mode. Now launch iTunes and restore your iPad with your custom firmware bundle by holding the shift button and clicking on “restore”.
5. Browse and Select the custom IPSW file you created (iPad1,1_4.2.1_8C148_Custom_Restore.ipsw) and click “open”.
6. Now wait for iTunes to complete the restore process. It may take 10-15 mini & it will reboot automatically.
Voila! Your iPad is now jailbroken on iOS 4.2.1.