Girallon has +7 BaB and a +4 Str modifier. It is Large sized.
Total is +12. Yes? Or am I missing something that gave him +14 total?
http://paizo.com/pathfinderRPG/prd/monsters/girallon.html#girallon
4 arms?
That's a reasonable guess. Guess I'll check the Xill and marilith for that.
It does not seem that the xill or marilith enjoy the same higher CMB as the girallon.
There are quite a few CMB mistakes in the Bestiary, I've found.