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

USN-4488-1: X.Org X Server vulnerabilities

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Ubuntu Security Notice USN-4488-1
September 02, 2020

xorg-server, xorg-server-hwe-16.04, xorg-server-hwe-18.04 vulnerabilities
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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:

Several security issues were fixed in X.Org X Server.

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
input extension protocol. A local attacker could possibly use this issue to
escalate privileges. (CVE-2020-14346)

Jan-Niklas Sohn discovered that the X.Org X Server incorrectly initialized
memory. A local attacker could possibly use this issue to obtain sensitive
information. (CVE-2020-14347)

Jan-Niklas Sohn discovered that the X.Org X Server incorrectly handled the
XkbSelectEvents function. A local attacker could possibly use this issue to
escalate privileges. (CVE-2020-14361)

Jan-Niklas Sohn discovered that the X.Org X Server incorrectly handled the
XRecordRegisterClients function. A local attacker could possibly use this
issue to escalate privileges. (CVE-2020-14362)

Update instructions:

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

Ubuntu 20.04 LTS:
xserver-xorg-core 2:1.20.8-2ubuntu2.3

Ubuntu 18.04 LTS:
xserver-xorg-core 2:1.19.6-1ubuntu4.5
xserver-xorg-core-hwe-18.04 2:1.20.8-2ubuntu2.2~18.04.2

Ubuntu 16.04 LTS:
xserver-xorg-core 2:1.18.4-0ubuntu0.9
xserver-xorg-core-hwe-16.04 2:1.19.6-1ubuntu4.1~16.04.3

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

References:
  https://usn.ubuntu.com/4488-1
CVE-2020-14346, CVE-2020-14347, CVE-2020-14361, CVE-2020-14362

Package Information:
  https://launchpad.net/ubuntu/+source/xorg-server/2:1.20.8-2ubuntu2.3
  https://launchpad.net/ubuntu/+source/xorg-server/2:1.19.6-1ubuntu4.5

  https://launchpad.net/ubuntu/+source/xorg-server-hwe-18.04/2:1.20.8-2ubuntu2.2~18.04.2
  https://launchpad.net/ubuntu/+source/xorg-server/2:1.18.4-0ubuntu0.9

  https://launchpad.net/ubuntu/+source/xorg-server-hwe-16.04/2:1.19.6-1ubuntu4.1~16.04.3