Can I jailbreak iPhone iOS 4.3.4 untethered?

Not yet. Although iOS 4.3.4 has already been jailbroken, the process is not simple and the result is a tethered jailbreak.

The iPhone Dev-Team and BigBoss among others have warned against updating to iOS 4.3.4 on any device if you wish to jailbreak. This update from Apple patches the PDF exploit employed by JailbreakMe 3.0 without adding any new functionality for iPhone users.

All hope is not lost. For those who have backed up their SHSH blobs the answer is to downgrade to iOS 4.3.3 firmware. If you have not saved these files act fast while Apple is still signing the iOS 4.3.3 firmware and save your SHSH blobs. After downgrading to iOS 4.3.3 you will be able to jailbreak untethered using JailbreakMe 3.0 or redsn0w.