A libx11 security update has been released for Ubuntu Linux 20.04 LTS, 22.04 LTS, 22.10, and 23.04.

[USN-6168-1] libx11 vulnerability

==========================================================================
Ubuntu Security Notice USN-6168-1
June 15, 2023

libx11 vulnerability
==========================================================================

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

- Ubuntu 23.04
- Ubuntu 22.10
- Ubuntu 22.04 LTS
- Ubuntu 20.04 LTS

Summary:

libx11 could be made to crash if it received specially crafted network
traffic.

Software Description:
- libx11: X11 client-side library

Details:

Gregory James Duck discovered that libx11 incorrectly handled certain
Request, Event, or Error IDs. If a user were tricked into connecting to a
malicious X Server, a remote attacker could possibly use this issue to
cause libx11 to crash, resulting in a denial of service.

Update instructions:

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

Ubuntu 23.04:
libx11-6 2:1.8.4-2ubuntu0.2

Ubuntu 22.10:
libx11-6 2:1.8.1-2ubuntu0.2

Ubuntu 22.04 LTS:
libx11-6 2:1.7.5-1ubuntu0.2

Ubuntu 20.04 LTS:
libx11-6 2:1.6.9-2ubuntu1.5

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

References:
https://ubuntu.com/security/notices/USN-6168-1
CVE-2023-3138

Package Information:
https://launchpad.net/ubuntu/+source/libx11/2:1.8.4-2ubuntu0.2
https://launchpad.net/ubuntu/+source/libx11/2:1.8.1-2ubuntu0.2
https://launchpad.net/ubuntu/+source/libx11/2:1.7.5-1ubuntu0.2
https://launchpad.net/ubuntu/+source/libx11/2:1.6.9-2ubuntu1.5