The xen packages contain administration tools and the xend service for managing the kernel-xen kernel for virtualization on Red Hat Enterprise Linux. A heap buffer overflow flaw was found in the way QEMU"s NE2000 NIC emulation implementation handled certain packets received over the network. A privileged user inside a guest could use this flaw to crash the QEMU instance or potentially execute arbitrary code on the host. Red Hat would like to thank Qinghao Tang of QIHU 360 Inc. for reporting this issue. All xen users are advised to upgrade to these updated packages, which contain a backported patch to correct this issue. After installing the updated packages, all running fully-virtualized guests must be restarted for this update to take effect.