It can vary. Looking at it, it could just be the finish cracked and has bent a bit.
I would not worry about it unless it's causing neck-shift issues, then that indicates there might be loose wood. The only way to fix is to inject glue and to clamp, but that's not something to attempt unless you are comfortable with it.
Given the looks of it, I'd just let it be. Many of my guitars have cracks like that, It seems 90% of the time, the crack is just in the finish, not in the wood. Tends to happen a lot to lighter woods like Basswood (which my Jag-Stang, Bass VI, and your Jazzmaster are made of).
