RHSA-2012:1234 - Security Advisory

Topic

Updated qemu-kvm packages that fix one security issue are now available for
Red Hat Enterprise Linux 6.

The Red Hat Security Response Team has rated this update as having
important security impact. A Common Vulnerability Scoring System (CVSS)
base score, which gives a detailed severity rating, is available from the
CVE link in the References section.

Description

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.

A flaw was found in the way QEMU handled VT100 terminal escape sequences
when emulating certain character devices. A guest user with privileges to
write to a character device that is emulated on the host using a virtual
console back-end could use this flaw to crash the qemu-kvm process on the
host or, possibly, escalate their privileges on the host. (CVE-2012-3515)

This flaw did not affect the default use of KVM. Affected configurations
were:

• When guests were started from the command line ("/usr/libexec/qemu-kvm")

without the "-nodefaults" option, and also without specifying a
serial or parallel device, or a virtio-console device, that specifically
does not use a virtual console (vc) back-end. (Note that Red Hat does not
support invoking "qemu-kvm" from the command line without "-nodefaults" on
Red Hat Enterprise Linux 6.)

• Guests that were managed via libvirt, such as when using Virtual Machine

Manager (virt-manager), but that have a serial or parallel device, or a
virtio-console device, that uses a virtual console back-end. By default,
guests managed via libvirt will not use a virtual console back-end
for such devices.

Red Hat would like to thank the Xen project for reporting this issue.

All users of qemu-kvm should upgrade to these updated packages, which
resolve this issue. 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.

Solution

Before applying this update, make sure all previously-released errata
relevant to your system have been applied.

This update is available via the Red Hat Network. Details on how to
use the Red Hat Network to apply this update are available at
https://access.redhat.com/knowledge/articles/11258

Affected Products

• Red Hat Enterprise Linux Server 6 x86_64
• Red Hat Enterprise Linux for x86_64 - Extended Update Support 6.3 x86_64
• Red Hat Enterprise Linux Server - Extended Life Cycle Support 6 x86_64
• Red Hat Enterprise Linux Workstation 6 x86_64
• Red Hat Enterprise Linux Desktop 6 x86_64
• Red Hat Enterprise Linux for Scientific Computing 6 x86_64
• Red Hat Enterprise Linux Server from RHUI 6 x86_64
• Red Hat Enterprise Linux Server - Extended Update Support from RHUI 6.3 x86_64
• Red Hat Enterprise Linux Server - Extended Life Cycle Support Extension 6 x86_64

Fixes

• BZ - 851252 - CVE-2012-3515 qemu: VT100 emulation vulnerability

CVEs

• CVE-2012-3515

References

• https://access.redhat.com/security/updates/classification/#important