Buffer overflow in hw/scsi-disk.c in the SCSI subsystem in QEMU before 0.15.2, as used by Xen, might allow local guest users with permission to access the CD-ROM to cause a denial of service (guest crash) via a crafted SAI READ CAPACITY SCSI command. NOTE: this is only a vulnerability when root has manually modified certain permissions or ACLs.
https://bugzilla.redhat.com/show_bug.cgi?id=736038
http://www.redhat.com/support/errata/RHSA-2011-1401.html