Buffer overflow in the SCSI implementation in QEMU, as used in Xen, when a SCSI controller has more than 256 attached devices, allows local users to gain privileges via a small transfer buffer in a REPORT LUNS command.
The qemu guest agent in Qemu 1.4.1 and earlier, as used by Xen, when started in daemon mode, uses weak permissions for certain files, which allows local users to read and write to these files.