The Dev Team has been using incomplete code-signing attacks to find and perform untethered jailbreaks on iOS devices that were running iOS 4.1 and up but this exploit has been patched with the latest release iOS 4.3.4. This was done in reaction to Comex’s JailbreakMe 3.0 tool that used a PDF exploit in iOS 4.3.3 to jailbreak all iOS devices including the iPad 2.
I0n1c who is actually Stefan Esser an independent iOS hacker has been talking about this on Twitter. He stated that incomplete code signing attacks were used for all untether exploits from at least iOS 4.1.0. In addition to this iOS 4.3.4 also adds code to dyld to detect attacks with binaries using incomplete code signing. He went on to say that iOS 4.3.4 does not only fix JailbreakMe 3.0 as announced but also silently kills the ndrv_setspec () integer overflow.

What this all means to the average person is that iOS 4.3.4 won’t be receiving an untethered jailbreak anytime soon. A significant consequence of course is that all future iOS devices that are sold by Apple Stores will come with iOS 4.3.4 which they won’t be able to jailbreak. What this will mean is that if you buy one of these you will have to live without Cydia until an untethered jailbreak solution is found.
If you have a jailbroken idevice you are advised to stay away from iOS 4.3.4. There is a tethered jailbreak solution available via Redsn0w and Pwnage Tool but with this you have to connect your iOS device to your PC every time you restart it.