A critical vulnerability in the widely used Xen hypervisor allows attackers to break out of a guest operating system running inside a virtual machine and access the host system’s entire memory.
This is a serious violation of the security barrier enforced by the hypervisor and poses a particular threat to multi-tenant data centers where the customers’ virtualized servers share the same underlying hardware.
The open-source Xen hypervisor is used by cloud computing providers and virtual private server hosting companies, as well as by security-oriented operating systems like Qubes OS.
The new vulnerability affects Xen 4.8.x, 4.7.x, 4.6.x, 4.5.x, and 4.4.x and has existed in the Xen code base for over four years. It was unintentionally introduced in December 2012 as part of a fix for a different issue.