The pciej_write function in hw/acpi_piix4.c in the PIIX4 Power Management emulation in qemu-kvm does not check if a device is hotpluggable before unplugging the PCI-ISA bridge, which allows privileged guest users to cause a denial of service (guest crash) and possibly execute arbitrary code by sending a crafted value to the 0xae08 (PCI_EJ_BASE) I/O port, which leads to a use-after-free related to "active qemu timers."

References

• https://nvd.nist.gov/vuln/detail/CVE-2011-1751
• https://bugzilla.redhat.com/show_bug.cgi?id=699773
• https://github.com/nelhage/virtunoid
• https://hermes.opensuse.org/messages/8572547
• https://www.ubuntu.com/usn/USN-1145-1/
• http://blog.nelhage.com/2011/08/breaking-out-of-kvm/
• http://git.kernel.org/?p=virt/kvm/qemu-kvm.git;a=commit;h=505597e4476a6bc219d0ec1362b760d71cb4fdca
• http://lists.nongnu.org/archive/html/qemu-devel/2011-05/msg01810.html
• http://lists.opensuse.org/opensuse-updates/2011-05/msg00043.html
• http://rhn.redhat.com/errata/RHSA-2011-0534.html
• http://secunia.com/advisories/44393
• http://secunia.com/advisories/44458
• http://secunia.com/advisories/44648
• http://secunia.com/advisories/44658
• http://secunia.com/advisories/44660
• http://secunia.com/advisories/44900
• http://www.openwall.com/lists/oss-security/2011/05/19/2
• http://www.osvdb.org/73395
• http://www.securityfocus.com/bid/47927
• https://access.redhat.com/errata/RHSA-2011:0534
• https://access.redhat.com/security/cve/CVE-2011-1751
• http://git.kernel.org/?p=virt/kvm/qemu-kvm.git%3Ba=commit%3Bh=505597e4476a6bc219d0ec1362b760d71cb4fdca