Multiple vulnerabilities has been discovered and corrected in libvirt:

An out-of-bounds read flaw was found in the way libvirt’s
qemuDomainGetBlockIoTune() function looked up the disk index in
a non-persistent (live) disk configuration while a persistent disk
configuration was being indexed. A remote attacker able to establish a
read-only connection to libvirtd could use this flaw to crash libvirtd
or, potentially, leak memory from the libvirtd process (CVE-2014-3633).

A denial of service flaw was found in the way libvirt’s
virConnectListAllDomains() function computed the number of used
domains. A remote attacker able to establish a read-only connection
to libvirtd could use this flaw to make any domain operations within
libvirt unresponsive (CVE-2014-3657).

The updated libvirt packages have been upgraded to the 1.1.3.6 version
and patched to resolve these security flaws.