The following updates has been release for Ubuntu Linux:

USN-3560-1: QEMU update
USN-3561-1: libvirt update

USN-3560-1: QEMU update

==========================================================================
Ubuntu Security Notice USN-3560-1
February 07, 2018

qemu update
==========================================================================

A security issue affects these releases of Ubuntu and its derivatives:

- Ubuntu 17.10
- Ubuntu 16.04 LTS
- Ubuntu 14.04 LTS

Summary:

Spectre mitigations were added to QEMU.

Software Description:
- qemu: Machine emulator and virtualizer

Details:

It was discovered that microprocessors utilizing speculative execution
and branch prediction may allow unauthorized memory reads via sidechannel
attacks. This flaw is known as Spectre. An attacker in the guest could use
this to expose sensitive guest information, including kernel memory.

This update allows QEMU to expose new CPU features added by microcode
updates to guests on amd64, i386, and s390x. On amd64 and i386, new CPU
models that match the updated microcode features were added with an -IBRS
suffix. Certain environments will require guests to be switched manually to
the new CPU models after microcode updates have been applied to the host.

Update instructions:

The problem can be corrected by updating your system to the following
package versions:

Ubuntu 17.10:
qemu-system 1:2.10+dfsg-0ubuntu3.4
qemu-system-s390x 1:2.10+dfsg-0ubuntu3.4
qemu-system-x86 1:2.10+dfsg-0ubuntu3.4

Ubuntu 16.04 LTS:
qemu-system 1:2.5+dfsg-5ubuntu10.20
qemu-system-s390x 1:2.5+dfsg-5ubuntu10.20
qemu-system-x86 1:2.5+dfsg-5ubuntu10.20

Ubuntu 14.04 LTS:
qemu-system 2.0.0+dfsg-2ubuntu1.38
qemu-system-x86 2.0.0+dfsg-2ubuntu1.38

After a standard system update you need to restart all QEMU virtual
machines to make all the necessary changes.

References:
https://www.ubuntu.com/usn/usn-3560-1
CVE-2017-5715

Package Information:
https://launchpad.net/ubuntu/+source/qemu/1:2.10+dfsg-0ubuntu3.4
https://launchpad.net/ubuntu/+source/qemu/1:2.5+dfsg-5ubuntu10.20
https://launchpad.net/ubuntu/+source/qemu/2.0.0+dfsg-2ubuntu1.38

USN-3561-1: libvirt update

==========================================================================
Ubuntu Security Notice USN-3561-1
February 07, 2018

libvirt update
==========================================================================

A security issue affects these releases of Ubuntu and its derivatives:

- Ubuntu 17.10
- Ubuntu 16.04 LTS
- Ubuntu 14.04 LTS

Summary:

Spectre mitigations were added to libvirt.

Software Description:
- libvirt: Libvirt virtualization toolkit

Details:

It was discovered that microprocessors utilizing speculative execution
and branch prediction may allow unauthorized memory reads via sidechannel
attacks. This flaw is known as Spectre. An attacker in the guest could use
this to expose sensitive guest information, including kernel memory.

This update allows libvirt to expose new CPU features added by microcode
updates to guests. On amd64 and i386, new CPU models that match the updated
microcode features were added with an -IBRS suffix. Certain environments
will require guests to be switched manually to the new CPU models after
microcode updates have been applied to the host.

Update instructions:

The problem can be corrected by updating your system to the following
package versions:

Ubuntu 17.10:
libvirt-bin 3.6.0-1ubuntu6.2
libvirt0 3.6.0-1ubuntu6.2

Ubuntu 16.04 LTS:
libvirt-bin 1.3.1-1ubuntu10.17
libvirt0 1.3.1-1ubuntu10.17

Ubuntu 14.04 LTS:
libvirt-bin 1.2.2-0ubuntu13.1.25
libvirt0 1.2.2-0ubuntu13.1.25

After a standard system update you need to reboot your computer to make
all the necessary changes.

References:
https://www.ubuntu.com/usn/usn-3561-1
CVE-2017-5715

Package Information:
https://launchpad.net/ubuntu/+source/libvirt/3.6.0-1ubuntu6.2
https://launchpad.net/ubuntu/+source/libvirt/1.3.1-1ubuntu10.17
https://launchpad.net/ubuntu/+source/libvirt/1.2.2-0ubuntu13.1.25