A Linux kernel security update has been released for Ubuntu Linux 14.04 ESM and 16.04 ESM.

USN-5591-1: Linux kernel vulnerability

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Ubuntu Security Notice USN-5591-1
August 31, 2022

linux-azure, linux-gcp, linux-hwe vulnerability
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A security issue affects these releases of Ubuntu and its derivatives:

- Ubuntu 16.04 ESM
- Ubuntu 14.04 ESM

Summary:

The system could be made to crash or run programs as an administrator.

Software Description:
- linux-azure: Linux kernel for Microsoft Azure Cloud systems
- linux-gcp: Linux kernel for Google Cloud Platform (GCP) systems
- linux-hwe: Linux hardware enablement (HWE) kernel

Details:

It was discovered that the virtual terminal driver in the Linux kernel did not properly handle VGA console font changes, leading to an out-of-bounds write. A local attacker could use this to cause a denial of service (system crash) or possibly execute arbitrary code.

Update instructions:

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

Ubuntu 16.04 ESM:
linux-image-4.15.0-1135-gcp 4.15.0-1135.151~16.04.2
linux-image-4.15.0-1150-azure 4.15.0-1150.165~16.04.1
linux-image-4.15.0-192-generic 4.15.0-192.203~16.04.1
linux-image-4.15.0-192-lowlatency 4.15.0-192.203~16.04.1
linux-image-azure 4.15.0.1150.137
linux-image-gcp 4.15.0.1135.129
linux-image-generic-hwe-16.04 4.15.0.192.179
linux-image-gke 4.15.0.1135.129
linux-image-lowlatency-hwe-16.04 4.15.0.192.179
linux-image-oem 4.15.0.192.179
linux-image-virtual-hwe-16.04 4.15.0.192.179

Ubuntu 14.04 ESM:
linux-image-4.15.0-1150-azure 4.15.0-1150.165~14.04.1
linux-image-azure 4.15.0.1150.119

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

ATTENTION: Due to an unavoidable ABI change the kernel updates have
been given a new version number, which requires you to recompile and
reinstall all third party kernel modules you might have installed.
Unless you manually uninstalled the standard kernel metapackages
(e.g. linux-generic, linux-generic-lts-RELEASE, linux-virtual,
linux-powerpc), a standard system upgrade will automatically perform
this as well.

References:
https://ubuntu.com/security/notices/USN-5591-1
CVE-2021-33656