The physdev_get_free_pirq hypercall in arch/x86/physdev.c in Xen 4.1.x and Citrix XenServer 6.0.2 and earlier uses the return value of the get_free_pirq function as an array index without checking that the return value indicates an error, which allows guest OS users to cause a denial of service (invalid memory write and host crash) and possibly gain privileges via unspecified vectors.
Improper Input Validation The product receives input or data, but it does
not validate or incorrectly validates that the input has the
properties that are required to process the data safely and
correctly.