A security researcher has released a tool that will untether iPhones and other devices running iOS 5.01. The tool, called Corona, takes advantage of a format string bug in a binary called racoon that s used when setting up IPSec connections. Corona is the work of a researcher who goes by the handle pod2g. He has posted a video demo of the untether tool in action, and the tool has been added to the redsn0w packages that will jailbreak and untether devices.
Source: https://threatpost.com/corona-ios-jailbreak-tool-released-010312/76048/