A X.Org X Server security update has been released for Ubuntu Linux 16.04 LTS.

[USN-5193-3] X.Org X Server vulnerabilities

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Ubuntu Security Notice USN-5193-3
July 27, 2023

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

- Ubuntu 16.04 LTS (Available with Ubuntu Pro)

Summary:

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

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

Details:

USN-5193-1 fixed several vulnerabilities in X.Org. This update provides
the corresponding update for Ubuntu 16.04 ESM.

Original advisory details:

Jan-Niklas Sohn discovered that the X.Org X Server incorrectly handled
certain inputs. An attacker could use this issue to cause the server to
crash, resulting in a denial of service, or possibly execute arbitrary
code and escalate privileges.

Update instructions:

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

Ubuntu 16.04 LTS (Available with Ubuntu Pro):
xserver-xorg-core-hwe-16.04 2:1.19.6-1ubuntu4.1~16.04.6+esm5

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

References:
https://ubuntu.com/security/notices/USN-5193-3
https://ubuntu.com/security/notices/USN-5193-1
CVE-2021-4008, CVE-2021-4009, CVE-2021-4011