Linux Mint downloads (briefly) compromised

3.19 is a stable kernel, just not the 'official' stable one. It supported for quite some time by canonical and imo they are doing a good job.

Assuming mint is based on ubuntu lts you can install a 4.2 kernel via:
apt-get install --install-recommends linux-generic-lts-wily

but I have never used mint, so maybe this doesn't work there.