An invalid free flaw in the libxl driver in libvirt resulted in libvirt crashing if "virsh numatune" was run on an inactive domain. It may be possible, but unlikely, for an attacker to leverage this flaw for arbitrary code execution.
This issue affects the version of libvirt in Fedora 20. It does not affect the versions of libvirt in Red Hat Enterprise Linux 5 and 6 as those versions do not use libxl.
Embargo is not required; this bug is already public: