[USN-4966-1] libx11 vulnerability

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

libx11 vulnerability
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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