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

USN-5211-1: Linux kernel vulnerability

=========================================================================
Ubuntu Security Notice USN-5211-1
January 06, 2022

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:

Nadav Amit discovered that the hugetlb implementation in the Linux kernel
did not perform TLB flushes under certain conditions. A local attacker
could use this to leak or alter data from other processes that use huge
pages.

Update instructions:

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

Ubuntu 16.04 ESM:
linux-image-4.4.0-1099-kvm 4.4.0-1099.108
linux-image-4.4.0-1134-aws 4.4.0-1134.148
linux-image-4.4.0-218-generic 4.4.0-218.251
linux-image-4.4.0-218-lowlatency 4.4.0-218.251
linux-image-aws 4.4.0.1134.139
linux-image-generic 4.4.0.218.225
linux-image-kvm 4.4.0.1099.97
linux-image-lowlatency 4.4.0.218.225
linux-image-virtual 4.4.0.218.225

Ubuntu 14.04 ESM:
linux-image-3.13.0-189-generic 3.13.0-189.240
linux-image-3.13.0-189-generic-lpae 3.13.0-189.240
linux-image-3.13.0-189-lowlatency 3.13.0-189.240
linux-image-4.4.0-1098-aws 4.4.0-1098.103
linux-image-4.4.0-218-generic 4.4.0-218.251~14.04.1
linux-image-4.4.0-218-lowlatency 4.4.0-218.251~14.04.1
linux-image-aws 4.4.0.1098.96
linux-image-generic 3.13.0.189.198
linux-image-generic-lpae 3.13.0.189.198
linux-image-generic-lts-xenial 4.4.0.218.189
linux-image-lowlatency 3.13.0.189.198
linux-image-lowlatency-lts-xenial 4.4.0.218.189
linux-image-server 3.13.0.189.198
linux-image-virtual 3.13.0.189.198
linux-image-virtual-lts-xenial 4.4.0.218.189

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-5211-1
CVE-2021-4002