Eh, all that needs to happen is a few solid hits. A Tiger Claw Warblade could probably end it in a few rounds once he got to it. A Factotum could do something nutty, almost certainly. A true caster? Bah, they've got a dozen ways easy of killing a flying foe.
Now, I'm not saying it's EASY, just that it's probably only on the high end of CR 4. We're not looking at That Damn Crab mk 2 Spider Demon Edition, just a tough critter.