A bug was found in the way Xen handles cpuid instruction emulation during VM exits. An unprivileged guest user can potentially use this flaw to crash the guest.
This issue only affects systems running on x86 architecture with Intel processor and VMX virtualization extension enabled.
The versions of the Linux kernel as shipped with Red Hat Enterprise Linux 4, 6, and Red Hat Enterprise MRG are not affected. This has been addressed in Red Hat Enterprise Linux 5 via https://rhn.redhat.com/errata/RHSA-2011-0927.html.
Also, only systems running on x86 architecture with Intel processor and VMX
virtualization extension enabled are affected.
This issue has been addressed in following products:
Red Hat Enterprise Linux 5
Via RHSA-2011:0927 https://rhn.redhat.com/errata/RHSA-2011-0927.html