The untethered Jailbreak for 4.2.1 with Greenpois0n has been fixed with almost not flaw this time. The Jailbreak is as easy as it was before, maybe not as easy as Jailbreakme.com, but still, barely any work. Follow the instructions below.
1. Download Greenpois0n RC5 B4 for Windows or Mac from GreenPois0n
2. Restore your iDevice to 4.2.1 (if you need to preserve your baseband and you require and unlock DO THAT with TinyUmbrella)
3. Open up Greenpois0n
4. Connect your iDevice and make sure your computer recognizes it.
5. Go into DFU through Greenpois0n, follow the steps on screen.
6. After you are in DFU, hit "Jailbreak" on Greenpois0n
7. Your phone will do a bunch of crazy stuff, let it sit until it restarts and finishes.
8. Connect to Wifi
9. Open up your loader app, that you have now on your homescreen.
10. Download Cydia.
Greenpois0n RC5 B4:
4.2.1 Firmware(for any reason you need it):
iPod, iPhone and iPad Firmware Download
- iPod Touch 2G (all bootroms)
- iPod Touch 3G
- iPod Touch 4G
- iPad 1G
- iPhone 3Gs (all bootroms)
- iPhone 4
- iPhone 4 Verizon (_not_tested_)
- AppleTV 2