Qubes OS was also shown to have inherent hardware virtualization sandbox vulnerabilities described by Joanna Rutkowska in an interesting lecture.

There is likely a PoC around someplace if people dig a bit. =3

It happened in 2006 and never happened after that. I would consider it as secure as it gets.

	▲	Joel_Mckay 39 minutes ago \| parent [-]
		Sorry, can't recall the exact lecture... It was only interesting as I was looking at a toy project to see if metastability issues were solvable. Practically speaking, it only proved the folks at Sun were very smart people choosing an encrypted mmu. =3