libvirt is a C API for managing and interacting with the virtualization capabilities of Linux and other operating systems. libvirt also provides tools for remotely managing virtualized systems.
The libvirtd daemon was discovered to not properly check user connection permissions before performing certain privileged actions, such as requesting migration of an unprivileged guest domain to another system. A local user able to establish a read-only connection to libvirtd could use this flaw to perform actions that should be restricted to read-write connections. (CVE-2008-5086)
libvirt_proxy, a setuid helper application allowing non-privileged users to communicate with the hypervisor, was discovered to not properly validate user requests. Local users could use this flaw to cause a stack-based buffer overflow in libvirt_proxy, possibly allowing them to run arbitrary code with root privileges. (CVE-2009-0036)
All users are advised to upgrade to these updated packages, which contain backported patches which resolve these issues. After installing the update, libvirtd must be restarted manually (for example, by issuing a "service libvirtd restart" command), and guest systems rebooted, for this change to take effect.