The qcow2_open function in the (block/qcow2.c) in QEMU before 1.7.2 and 2.x before 2.0.0 allows local users to cause a denial of service (NULL pointer dereference) via a crafted image which causes an error, related to the initialization of the snapshot_offset and nb_snapshots fields.
http://rhn.redhat.com/errata/RHSA-2014-0420.html
http://rhn.redhat.com/errata/RHSA-2014-0421.html
https://bugzilla.redhat.com/show_bug.cgi?id=1078232