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

USN-5039-1: Linux kernel vulnerability

=========================================================================
Ubuntu Security Notice USN-5039-1
August 12, 2021

linux, linux-aws, linux-kvm, linux-lts-xenial vulnerability
=========================================================================
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: Linux kernel
- linux-aws: Linux kernel for Amazon Web Services (AWS) systems
- linux-kvm: Linux kernel for cloud environments
- linux-lts-xenial: Linux hardware enablement kernel from Xenial for Trusty

Details:

Andy Nguyen discovered that the netfilter subsystem in the Linux kernel
contained an out-of-bounds write in its setsockopt() implementation. 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-4.4.0-1096-kvm 4.4.0-1096.105
linux-image-4.4.0-1131-aws 4.4.0-1131.145
linux-image-4.4.0-213-generic 4.4.0-213.245
linux-image-4.4.0-213-lowlatency 4.4.0-213.245
linux-image-aws 4.4.0.1131.136
linux-image-generic 4.4.0.213.220
linux-image-kvm 4.4.0.1096.94
linux-image-lowlatency 4.4.0.213.220
linux-image-virtual 4.4.0.213.220

Ubuntu 14.04 ESM:
linux-image-3.13.0-187-generic 3.13.0-187.238
linux-image-3.13.0-187-generic-lpae 3.13.0-187.238
linux-image-3.13.0-187-lowlatency 3.13.0-187.238
linux-image-4.4.0-1095-aws 4.4.0-1095.100
linux-image-4.4.0-213-generic 4.4.0-213.245~14.04.1
linux-image-4.4.0-213-lowlatency 4.4.0-213.245~14.04.1
linux-image-aws 4.4.0.1095.93
linux-image-generic 3.13.0.187.196
linux-image-generic-lpae 3.13.0.187.196
linux-image-generic-lts-xenial 4.4.0.213.186
linux-image-lowlatency 3.13.0.187.196
linux-image-lowlatency-lts-xenial 4.4.0.213.186
linux-image-server 3.13.0.187.196
linux-image-virtual 3.13.0.187.196
linux-image-virtual-lts-xenial 4.4.0.213.186

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-5039-1
CVE-2021-22555