As expected, iOS 4.0.1 has been jailbroken within hours of its release. While the iPhone 4 and 3GS users will have to wait for a new jailbreak tool, iPhone 3G can go ahead and jailbreak their phone on iOS 4.0.1 using Redsn0w 0.9.5b5-5.
According to iPhone dev team, you must hold back from updating to iOS 4.0.1
Although you can jailbreak iOS 4.0.1, you should hold off on updating to iOS 4.0.1. In fact don’t even update to iOS 4.0.1 yet, because it’s just a small update. Apple will be releasing an iOS 4.1 download (no ETA on that) which will be a bigger update, so I recommend waiting for that.
In case you can’t wait you can go ahead and update to iOS 4.0.1 only if you are using iPhone 3G.
How to Jailbreak iPhone 3G iOS 4.0.1 using Redsn0w 0.9.5b5-5
1. Download iOS 4.0.1 for your version of iPhone.
2. Update to this latest firmware using the IPSW file you just downloaded.
4. Start Redsn0w 0.9.5b5-5 and point it to iOS 4 (Final Version), and not iOS 4.0.1 firmware file to proceed with the jailbreak.
5. Select “Install Cydia” and click “Next”.
6. Now make sure your device is both OFF and PLUGGED IN to the computer before you click “Next”.
7. Connect your device in recovery mode by pressing the Power and buttons continuously.
8. Wait for RedSn0w to jailbreak your iPhone 3G.
9. Unlock iPhone 3G iOS 4.0.1 using Ultrasn0w 0.93
Disclaimer: This guide is just for informational and educative purposes only. We are not responsible for any loss of important data or malfunctioning of your iPhone.