Updated libvirt packages that fix one security issue and three bugs are now available for Red Hat Enterprise Linux 6. The Red Hat Security Response Team has rated this update as having Moderate security impact. A Common Vulnerability Scoring System base score, which gives a detailed severity rating, is available from the CVE link in the References section. 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 found that libvirt passes the XML_PARSE_NOENT flag when parsing XML documents using the libxml2 library, in which case all XML entities in the parsed documents are expanded. A user able to force libvirtd to parse an XML document with an entity pointing to a special file that blocks on read access could use this flaw to cause libvirtd to hang indefinitely, resulting in a denial of service on the system. Red Hat would like to thank the upstream Libvirt project for reporting this issue. Upstream acknowledges Daniel P. Berrange and Richard Jones as the original reporters. This update also fixes the following bugs: * When hot unplugging a virtual CPU , libvirt kept a pointer to already freed memory if the vCPU was pinned to a host CPU. Consequently, when reading the CPU pinning information, libvirt terminated unexpectedly due to an attempt to access this memory. This update ensures that libvirt releases the pointer to the previously allocated memory when a vCPU is being hot unplugged, and it no longer crashes in this situation. * Previously, libvirt passed an incorrect argument to the "tc" command when setting quality of service on a network interface controller . As a consequence, QoS was applied only to IP traffic. With this update, libvirt constructs the "tc" command correctly so that QoS is applied to all traffic as expected. * When using the sanlock daemon for managing access to shared storage, libvirt expected all QEMU domains to be registered with sanlock. However, if a QEMU domain was started prior to enabling sanlock, the domain was not registered with sanlock. Consequently, migration of a virtual machine from such a QEMU domain failed with a libvirt error. With this update, libvirt verifies whether a QEMU domain process is registered with sanlock before it starts working with the domain, ensuring that migration of virtual machines works as expected. All libvirt users are advised to upgrade to these updated packages, which contain backported patches to correct these issues. After installing the updated packages, libvirtd will be restarted automatically.