USN-3560-1: QEMU update

7 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 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

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.