The problem is that the kernel (3.8) has not been receiving any more security updates for days.
We should still stick with the cloud-images.ubuntu.com boxes while the problem gets fixed because the files.vagrantup.com boxes lack months/years worth of security updates for the entire OS, unless a user manually updates the OS.
Ben Howard (utlemming) fixed this on 2014-08-20 by reverting the boxes to the precise HWE stack. That works, we never needed a newer HWE stack. I verified that the VIrtualBox Guest Additions still work.
Reported to our upstream, the Ubuntu project. https://bugs.launchpad.net/ubuntu/+bug/1354839 It's being worked on by a Canonical employee.
The problem is that the kernel (3.8) has not been receiving any more security updates for days.
We should still stick with the cloud-images.ubuntu.com boxes while the problem gets fixed because the files.vagrantup.com boxes lack months/years worth of security updates for the entire OS, unless a user manually updates the OS.