Xen 4.2.x, 4.1.x, and earlier, when the hypervisor is running "under memory pressure" and the Xen Security Module (XSM) is enabled, uses the wrong ordering of operations when extending the per-domain event channel tracking table, which causes a use-after-free and allows local guest kernels to inject arbitrary events and gain privileges via unspecified vectors.
oxenstored in Xen 4.1.x, Xen 4.2.x, and xen-unstable does not properly consider the state of the Xenstore ring during read operations, which allows guest OS users to cause a denial of service (daemon crash and host-control outage, or memory consumption) or obtain sensitive control-plane data by leveraging guest administrative access.
The do_hvm_op function in xen/arch/x86/hvm/hvm.c in Xen 4.2.x on the x86_32 platform does not prevent HVM_PARAM_NESTEDHVM (aka nested virtualization) operations, which allows guest OS users to cause a denial of service (long-duration page mappings and host OS crash) by leveraging administrative access to an HVM guest in a domain with a large number of VCPUs.
The AMD IOMMU support in Xen 4.2.x, 4.1.x, 3.3, and other versions, when using AMD-Vi for PCI passthrough, uses the same interrupt remapping table for the host and all guests, which allows guests to cause a denial of service by injecting an interrupt into other guests.
Xen 4.2.x, 4.1.x, and 4.0, when using Intel VT-d for PCI passthrough, does not properly configure VT-d when supporting a device that is behind a legacy PCI Bridge, which allows local guests to cause a denial of service to other guests by injecting an interrupt.
Heap-based buffer overflow in QEMU 0.8.2, as used in Xen and possibly other products, allows local users to execute arbitrary code via crafted data in the "net socket listen" option, aka QEMU "net socket" heap overflow. NOTE: some sources have used CVE-2007-1321 to refer to this issue as part of "NE2000 network driver and the socket code," but this is the correct identifier for the individual net socket listen vulnerability.