ITunes says 5.1 is the current firmware for my iPhone 4?

Apparently it is possible to upgrade to iOS 6 on the iPhone 4, however both my iPhone and my iTunes says that 5.1 is the current firmware available.

At first I figured it was because my iTunes was severely out of date, so I updated it to the current version, however it still says the same thing.

I have an iPhone 4 GSM model currently running iOS 5.1.

Any way I can get my iTunes or my iPhone to realize that I can in fact upgrade to iOS 6? (unless I'm greatly misinformed =P)

Thanks in advance

Added (1). I should also mention that I'm jailbroken

Your current software is 5.1 it is probably saying, and you don't need the computer to upgrade. Just go to Settings: General: Software Update than do the update take like 30 mins more or less

Restore in itunes and it will update to ios 6