A X.Org X Server security update has been released for Ubuntu Linux 20.04 LTS, 18.04 LTS, and 16.04 LTS.

USN-4490-1: X.Org X Server vulnerability

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Ubuntu Security Notice USN-4490-1
September 08, 2020

xorg-server, xorg-server-hwe-16.04, xorg-server-hwe-18.04 vulnerability
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A security issue affects these releases of Ubuntu and its derivatives:

- Ubuntu 20.04 LTS
- Ubuntu 18.04 LTS
- Ubuntu 16.04 LTS

Summary:

X.Org X Server could be made to crash or run programs if it received
specially crafted input.

Software Description:
- xorg-server: X.Org X11 server
- xorg-server-hwe-18.04: X.Org X11 server
- xorg-server-hwe-16.04: X.Org X11 server

Details:

Jan-Niklas Sohn discovered that the X.Org X Server incorrectly handled the
XkbSetNames function. A local attacker could possibly use this issue to
escalate privileges.

Update instructions:

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

Ubuntu 20.04 LTS:
xserver-xorg-core 2:1.20.8-2ubuntu2.4

Ubuntu 18.04 LTS:
xserver-xorg-core 2:1.19.6-1ubuntu4.6
xserver-xorg-core-hwe-18.04 2:1.20.8-2ubuntu2.2~18.04.3

Ubuntu 16.04 LTS:
xserver-xorg-core 2:1.18.4-0ubuntu0.10
xserver-xorg-core-hwe-16.04 2:1.19.6-1ubuntu4.1~16.04.4

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

References:
  https://usn.ubuntu.com/4490-1
CVE-2020-14345

Package Information:
  https://launchpad.net/ubuntu/+source/xorg-server/2:1.20.8-2ubuntu2.4
  https://launchpad.net/ubuntu/+source/xorg-server/2:1.19.6-1ubuntu4.6

  https://launchpad.net/ubuntu/+source/xorg-server-hwe-18.04/2:1.20.8-2ubuntu2.2~18.04.3
  https://launchpad.net/ubuntu/+source/xorg-server/2:1.18.4-0ubuntu0.10

  https://launchpad.net/ubuntu/+source/xorg-server-hwe-16.04/2:1.19.6-1ubuntu4.1~16.04.4