USN-3560-1: QEMU update

Ubuntu Security Notice USN-3560-1

7th February, 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


Spectre mitigations were added to QEMU.

Software description

  • qemu - Machine emulator and virtualizer


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 version:

Ubuntu 17.10:
qemu-system-x86 1:2.10+dfsg-0ubuntu3.4
qemu-system 1:2.10+dfsg-0ubuntu3.4
qemu-system-s390x 1:2.10+dfsg-0ubuntu3.4
Ubuntu 16.04 LTS:
qemu-system-x86 1:2.5+dfsg-5ubuntu10.20
qemu-system 1:2.5+dfsg-5ubuntu10.20
qemu-system-s390x 1:2.5+dfsg-5ubuntu10.20
Ubuntu 14.04 LTS:
qemu-system-x86 2.0.0+dfsg-2ubuntu1.38
qemu-system 2.0.0+dfsg-2ubuntu1.38

To update your system, please follow these instructions:

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