Ubuntu 6289 Published by

A libx11 security update has been released for Ubuntu Linux 14.04 LTS, 16.04 LTS, and 18.04 LTS.

[USN-6168-2] libx11 vulnerability

Ubuntu Security Notice USN-6168-2
June 20, 2023

libx11 vulnerability
A security issue affects these releases of Ubuntu and its derivatives:

- Ubuntu 18.04 LTS (Available with Ubuntu Pro)
- Ubuntu 16.04 LTS (Available with Ubuntu Pro)
- Ubuntu 14.04 LTS (Available with Ubuntu Pro)


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

Software Description:
- libx11: X11 client-side library


USN-6168-1 fixed a vulnerability in libx11. This update provides
the corresponding update for Ubuntu 14.04 ESM, Ubuntu 16.04 ESM,
and Ubuntu 18.04 ESM.

Original advisory 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 18.04 LTS (Available with Ubuntu Pro):
libx11-6 2:1.6.4-3ubuntu0.4+esm1

Ubuntu 16.04 LTS (Available with Ubuntu Pro):
libx11-6 2:1.6.3-1ubuntu2.2+esm2

Ubuntu 14.04 LTS (Available with Ubuntu Pro):
libx11-6 2:1.6.2-1ubuntu2.1+esm3

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