This question already has an answer here:
I need the latest SSL security fix, as I'm running iOS 6.1.3. But, I don't have enough space to go to iOS 7 which is the only option iTunes and my phone are giving me to upgrade.
I have an 8 GB iPhone 4 with usually less than 100-200 MB free, and have deleted all apps and non-essential music/photos so I really don't have the space to go all the way to iOS 7 (I understand iOS 7 only takes a few hundred MB beyond that which iOS 6 occupies, but every little bit counts and I'm already driven crazy downloading photos of my daughter every few days because I've run out of room.)
Am I completely out of luck?