Ubuntu 16.04 LTS Temporarily Rebases To Linux 4.3
Ubuntu 16.04 LTS will end up using the Linux 4.4 kernel but while that version is still weeks away from release and being fixed up, Ubuntu "Xenial Xerus" users have the Linux 4.3 kernel upgrade, as confirmed by this week's kernel team news.
Linux 4.3 brought many exciting features but as is the case with new versions of the Linux kernel, Linux 4.4 is already much more exciting.
Linux 4.4 should be released in early January. Linux 4.5 will come after that, but with Ubuntu 16.04 being a Long Term Support release and due out in April, Canonical is playing it safe and aiming just for Linux 4.4.