=========================================================================Ubuntu Security Notice USN-4966-1
May 25, 2021

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

- Ubuntu 21.04
- Ubuntu 20.10
- Ubuntu 20.04 LTS
- Ubuntu 18.04 LTS

Summary:

libx11 could allow unintended access to services.

Software Description:
- libx11: X11 client-side library

Details:

It was discovered that libx11 incorrectly validated certain parameter
lengths. A remote attacker could possibly use this issue to trick libx11
into emitting extra X protocol requests.

Update instructions:

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

Ubuntu 21.04:
  libx11-6                        2:1.7.0-2ubuntu0.1

Ubuntu 20.10:
  libx11-6                        2:1.6.12-1ubuntu0.1

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

Ubuntu 18.04 LTS:
  libx11-6                        2:1.6.4-3ubuntu0.4

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

References:
  https://ubuntu.com/security/notices/USN-4966-1
  CVE-2021-31535

Package Information:
  https://launchpad.net/ubuntu/+source/libx11/2:1.7.0-2ubuntu0.1
  https://launchpad.net/ubuntu/+source/libx11/2:1.6.12-1ubuntu0.1
  https://launchpad.net/ubuntu/+source/libx11/2:1.6.9-2ubuntu1.2
  https://launchpad.net/ubuntu/+source/libx11/2:1.6.4-3ubuntu0.4