The libvirt library is a C API for managing and interacting with the virtualization capabilities of Linux and other operating systems. In addition, libvirt provides tools for remote management of virtualized systems. It was discovered that libvirt made certain invalid assumptions about dnsmasq"s command line options when setting up DNS masquerading for virtual machines, resulting in dnsmasq incorrectly processing network packets from network interfaces that were intended to be prohibited. This update includes the changes necessary to call dnsmasq with a new command line option, which was introduced to dnsmasq via RHSA-2013:0277. In order for libvirt to be able to make use of the new command line option , updated dnsmasq packages need to be installed. Refer to RHSA-2013:0277 for additional information. These updated libvirt packages include numerous bug fixes and enhancements. Space precludes documenting all of these changes in this advisory. Users are directed to the Red Hat Enterprise Linux 6.4 Technical Notes, linked to in the References, for information on the most significant of these changes. All users of libvirt are advised to upgrade to these updated packages, which fix these issues and add these enhancements. After installing the updated packages, libvirtd must be restarted for this update to take effect.