“Xenpwn is a toolkit for memory access tracing using hardware assisted virtualization. It runs as a normal user space application inside the management domain (dom0) of a Xen hypervisor and can be used to trace any memory accesses performed by another VM running on the same hypervisor. The toolkit uses libvmi for interaction with the Xen hypervisor API and relies on simutrace for efficient storage of memory traces. Xenpwn was used to discover double fetch vulnerabilities in the inter domain communication of the Xen hypervisor resulting in XSA 155. Further research on identifying double fetches in other software is still ongoing.[…]”