The following updates has been released for Ubuntu Linux:

USN-3755-1: GD vulnerabilities
USN-3756-1: Intel Microcode vulnerabilities

USN-3755-1: GD vulnerabilities

==========================================================================
Ubuntu Security Notice USN-3755-1
August 27, 2018

libgd2 vulnerabilities
==========================================================================

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

- Ubuntu 18.04 LTS
- Ubuntu 16.04 LTS
- Ubuntu 14.04 LTS

Summary:

Several security issues were fixed in GD.

Software Description:
- libgd2: GD Graphics Library

Details:

It was discovered that GD incorrectly handled certain images.
An attacker could possibly use this issue to execute arbitrary code.
(CVE-2018-1000222)

It was discovered that GD incorrectly handled certain GIF files.
An attacker could possibly use this issue to cause a denial of service.
(CVE-2018-5711)

Update instructions:

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

Ubuntu 18.04 LTS:
  libgd-tools 2.2.5-4ubuntu0.2
  libgd3 2.2.5-4ubuntu0.2

Ubuntu 16.04 LTS:
  libgd-tools 2.1.1-4ubuntu0.16.04.10
  libgd3 2.1.1-4ubuntu0.16.04.10

Ubuntu 14.04 LTS:
  libgd-tools 2.1.0-3ubuntu0.10
  libgd3 2.1.0-3ubuntu0.10

In general, a standard system update will make all the necessary
changes.

References:
  https://usn.ubuntu.com/usn/usn-3755-1
  CVE-2018-1000222, CVE-2018-5711

Package Information:
  https://launchpad.net/ubuntu/+source/libgd2/2.2.5-4ubuntu0.2
  https://launchpad.net/ubuntu/+source/libgd2/2.1.1-4ubuntu0.16.04.10
  https://launchpad.net/ubuntu/+source/libgd2/2.1.0-3ubuntu0.10

USN-3756-1: Intel Microcode vulnerabilities

=========================================================================
Ubuntu Security Notice USN-3756-1
August 27, 2018

intel-microcode vulnerabilities
=========================================================================
A security issue affects these releases of Ubuntu and its derivatives:

- Ubuntu 18.04 LTS
- Ubuntu 16.04 LTS
- Ubuntu 14.04 LTS

Summary:

The system could be made to expose sensitive information.

Software Description:
- intel-microcode: Processor microcode for Intel CPUs

Details:

It was discovered that memory present in the L1 data cache of an Intel CPU
core may be exposed to a malicious process that is executing on the CPU
core. This vulnerability is also known as L1 Terminal Fault (L1TF). A local
attacker in a guest virtual machine could use this to expose sensitive
information (memory from other guests or the host OS). (CVE-2018-3646)

Jann Horn and Ken Johnson discovered that microprocessors utilizing
speculative execution of a memory read may allow unauthorized memory reads
via a sidechannel attack. This flaw is known as Spectre Variant 4. A local
attacker could use this to expose sensitive information, including kernel
memory. (CVE-2018-3639)

Zdenek Sojka, Rudolf Marek, Alex Zuepke, and Innokentiy Sennovskiy
discovered that microprocessors that perform speculative reads of
system registers may allow unauthorized disclosure of system parameters
via a sidechannel attack. This vulnerability is also known as Rogue
System Register Read (RSRE). An attacker could use this to expose
sensitive information. (CVE-2018-3640)

Update instructions:

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

Ubuntu 18.04 LTS:
intel-microcode 3.20180807a.0ubuntu0.18.04.1

Ubuntu 16.04 LTS:
intel-microcode 3.20180807a.0ubuntu0.16.04.1

Ubuntu 14.04 LTS:
intel-microcode 3.20180807a.0ubuntu0.14.04.1

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

References:
https://usn.ubuntu.com/usn/usn-3756-1
CVE-2018-3639, CVE-2018-3640, CVE-2018-3646

Package Information:
https://launchpad.net/ubuntu/+source/intel-microcode/3.20180807a.0ubuntu0.18.04.1
https://launchpad.net/ubuntu/+source/intel-microcode/3.20180807a.0ubuntu0.16.04.1
https://launchpad.net/ubuntu/+source/intel-microcode/3.20180807a.0ubuntu0.14.04.1