A X.Org X Server security update has been released for Ubuntu Linux 14.04 ESM.

USN-4656-2: X.Org X Server vulnerabilities

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Ubuntu Security Notice USN-4656-2
December 07, 2020

xorg-server vulnerabilities
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A security issue affects these releases of Ubuntu and its derivatives:

- Ubuntu 14.04 ESM

Summary:

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

Software Description:
- xorg-server: X.Org X11 server

Details:

USN-4656-1 fixed several vulnerabilities in X.Org. This update provides
the corresponding update for Ubuntu 14.04 ESM.

Original advisory details:

Jan-Niklas Sohn discovered that the X.Org X Server XKB extension
incorrectly handled certain inputs. 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 14.04 ESM:
xserver-xorg-core 2:1.15.1-0ubuntu2.11+esm3

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

References:
  https://usn.ubuntu.com/4656-2
  https://usn.ubuntu.com/4656-1
CVE-2020-14360, CVE-2020-25712