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."

The remote Oracle Linux 6 host has packages installed that are affected by multiple vulnerabilities as referenced in the ELSA-2011-0534 advisory.

  - Multiple heap-based buffer overflows in the virtio-blk driver (hw/virtio-blk.c) in qemu-kvm 0.14.0 allow     local guest users to cause a denial of service (guest crash) and possibly gain privileges via a (1) write     request to the virtio_blk_handle_write function or (2) read request to the virtio_blk_handle_read function     that is not properly aligned. (CVE-2011-1750)

  - 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. (CVE-2011-1751)

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

By causing a hot-unplug of the pci-isa bridge from within guests the qemu process could access already freed memory. A privileged user inside the guest could exploit that to crash the guest instance or potentially execute arbitrary code on the host (CVE-2011-1751).

The virtio-blk driver did not properly validate read and write request. A privileged user inside the guest could exploit that to cause a heap corruption and crash the guest instance or potentially execute arbitrary code on the host (CVE-2011-1750).

Updated qemu-kvm packages that fix two security issues, several bugs, and add various enhancements are now available for Red Hat Enterprise Linux 6.

The Red Hat Security Response Team has rated this update as having important security impact. Common Vulnerability Scoring System (CVSS) base scores, which give detailed severity ratings, are available for each vulnerability from the CVE links in the References section.

KVM (Kernel-based Virtual Machine) is a full virtualization solution for Linux on AMD64 and Intel 64 systems. qemu-kvm is the user-space component for running virtual machines using KVM.

It was found that the virtio-blk driver in qemu-kvm did not properly validate read and write requests from guests. A privileged guest user could use this flaw to crash the guest or, possibly, execute arbitrary code on the host. (CVE-2011-1750)

It was found that the PIIX4 Power Management emulation layer in qemu-kvm did not properly check for hot plug eligibility during device removals. A privileged guest user could use this flaw to crash the guest or, possibly, execute arbitrary code on the host.
(CVE-2011-1751)

Red Hat would like to thank Nelson Elhage for reporting CVE-2011-1751.

This update also fixes several bugs and adds various enhancements.
Documentation for these bug fixes and enhancements will be available shortly from the Technical Notes document, linked to in the References section.

All users of qemu-kvm should upgrade to these updated packages, which contain backported patches to resolve these issues, and fix the bugs and add the enhancements noted in the Technical Notes. After installing this update, shut down all running virtual machines. Once all virtual machines have shut down, start them again for this update to take effect.

The remote host is affected by the vulnerability described in GLSA-201210-04 (qemu-kvm: Multiple vulnerabilities)

    Multiple vulnerabilities have been discovered in qemu-kvm. Please review       the CVE identifiers referenced below for details.
  Impact :

    These vulnerabilities allow a remote attacker to cause a Denial of       Service condition on the host server or qemu process, might allow for       arbitrary code execution or a symlink attack when qemu-kvm is in snapshot       mode.
  Workaround :

    There is no known workaround at this time.

KVM (Kernel-based Virtual Machine) is a full virtualization solution for Linux on AMD64 and Intel 64 systems. qemu-kvm is the user-space component for running virtual machines using KVM.

It was found that the virtio-blk driver in qemu-kvm did not properly validate read and write requests from guests. A privileged guest user could use this flaw to crash the guest or, possibly, execute arbitrary code on the host. (CVE-2011-1750)

It was found that the PIIX4 Power Management emulation layer in qemu-kvm did not properly check for hot plug eligibility during device removals. A privileged guest user could use this flaw to crash the guest or, possibly, execute arbitrary code on the host.
(CVE-2011-1751)

This update also fixes several bugs and adds various enhancements.

All users of qemu-kvm should upgrade to these updated packages, which contain backported patches to resolve these issues, and fix the bugs and add the enhancements.

After installing this update, shut down all running virtual machines.
Once all virtual machines have shut down, start them again for this update to take effect.

It was discovered that QEMU did not properly perform validation of I/O operations from the guest which could lead to heap corruption. An attacker could exploit this to cause a denial of service of the guest or possibly execute code with the privileges of the user invoking the program. (CVE-2011-1750)

Nelson Elhage discoverd that QEMU did not properly handle memory when removing ISA devices. An attacker could exploit this to cause a denial of service of the guest or possibly execute code with the privileges of the user invoking the program. (CVE-2011-1751)

When using QEMU with libvirt or virtualization management software based on libvirt such as Eucalyptus and OpenStack, QEMU guests are individually isolated by an AppArmor profile by default in Ubuntu.

Note that Tenable Network Security has extracted the preceding description block directly from the Ubuntu security advisory. Tenable has attempted to automatically clean and format it as much as possible without introducing additional issues.

Nelson Elhage discovered that incorrect memory handling during the removal of ISA devices in KVM, a solution for full virtualization on x86 hardware, could lead to denial of service or the execution of arbitrary code.

The following bugs have been fixed :

  - By causing a hot-unplug of the pci-isa bridge from     within guests the qemu process could access already     freed memory. A privileged user inside the guest could     exploit that to crash the guest instance or potentially     execute arbitrary code on the host. (CVE-2011-1751)

  - The virtio-blk driver did not properly validate read and     write request. A privileged user inside the guest could     exploit that to cause a heap corruption and crash the     guest instance or potentially execute arbitrary code on     the host. (CVE-2011-1750)

ID	Name	Product	Family	Severity
181056	Oracle Linux 6 : qemu-kvm (ELSA-2011-0534)	Nessus	Oracle Linux Local Security Checks	high
75887	openSUSE Security Update : kvm (openSUSE-SU-2011:0510-1)	Nessus	SuSE Local Security Checks	high
75566	openSUSE Security Update : kvm (openSUSE-SU-2011:0510-1)	Nessus	SuSE Local Security Checks	high
63980	RHEL 6 : qemu-kvm (RHSA-2011:0534)	Nessus	Red Hat Local Security Checks	high
62634	GLSA-201210-04 : qemu-kvm: Multiple vulnerabilities	Nessus	Gentoo Local Security Checks	high
61047	Scientific Linux Security Update : qemu-kvm on SL6.x x86_64	Nessus	Scientific Linux Local Security Checks	high
55108	Ubuntu 10.04 LTS / 10.10 / 11.04 : qemu-kvm vulnerabilities (USN-1145-1)	Nessus	Ubuntu Local Security Checks	high
55029	Debian DSA-2241-1 : qemu-kvm - implementation error	Nessus	Debian Local Security Checks	high
54640	SuSE 11.1 Security Update : kvm (SAT Patch Number 4574)	Nessus	SuSE Local Security Checks	high

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