I agree that is an old kernel. How many patches have been made since the 3.10 kernel?
$ git rev-list v3.10..HEAD --count 283077
Is this Sony or Android still using an older kernel?
I think Android is at 3.18. Security patches get backported as and when necessary, though.
Marshmallow is on 3.18. Nougat is on 4.4.
That is a big difference, do any of Sony phones run nougat?