The virtio_net_bad_features function in hw/virtio-net.c in the virtio-net driver in the Linux kernel before 2.6.26, when used on a guest OS in conjunction with qemu-kvm 0.11.0 or KVM 83, allows remote attackers to cause a denial of service (guest OS crash, and an associated qemu-kvm process exit) by sending a large amount of network traffic to a TCP port on the guest OS, related to a virtio-net whitelist that includes an improper implementation of TCP Segment Offloading (TSO).
The x86 emulator in KVM 83, when a guest is configured for Symmetric Multiprocessing (SMP), does not properly restrict writing of segment selectors to segment registers, which might allow guest OS users to cause a denial of service (guest OS crash) or gain privileges on the guest OS by leveraging access to a (1) IO port or (2) MMIO region, and replacing an instruction in between emulator entry and instruction fetch.
The x86 emulator in KVM 83, when a guest is configured for Symmetric Multiprocessing (SMP), does not use the Current Privilege Level (CPL) and I/O Privilege Level (IOPL) to restrict instruction execution, which allows guest OS users to cause a denial of service (guest OS crash) or gain privileges on the guest OS by leveraging access to a (1) IO port or (2) MMIO region, and replacing an instruction in between emulator entry and instruction fetch, a related issue to CVE-2010-0298.