A new release of the Ubuntu Cloud Images for stable Ubuntu release 21.04 (Hirsute Hippo) is available at [1]. These new images superseded the existing images [2]. Images are available for download or immediate use on EC2 via publish AMI ids. Users who wish to update their existing installations can do so with:
   'sudo apt-get update && sudo apt-get dist-upgrade && sudo reboot'.

The following packages have been updated. Please see the full changelogs
for a complete listing of changes:
 * linux-meta: 5.11.0.44.44 => 5.11.0.46.46 
 * linux-signed: 5.11.0-44.48 => 5.11.0-46.51 
 * openssh: 1:8.4p1-5ubuntu1.1 => 1:8.4p1-5ubuntu1.2 
 * systemd: 247.3-3ubuntu3.6 => 247.3-3ubuntu3.7 


The following is a complete changelog for this image.
new: {'linux-headers-5.11.0-46-generic': '5.11.0-46.51', 'linux-modules-5.11.0-46-generic': '5.11.0-46.51', 'linux-headers-5.11.0-46': '5.11.0-46.51'}
removed: {'linux-modules-5.11.0-44-generic': '5.11.0-44.48', 'linux-headers-5.11.0-44': '5.11.0-44.48', 'linux-headers-5.11.0-44-generic': '5.11.0-44.48'}
changed: ['libnss-systemd:amd64', 'libpam-systemd:amd64', 'libsystemd0:amd64', 'libudev1:amd64', 'linux-headers-generic', 'linux-headers-virtual', 'linux-image-5.11.0-46-generic', 'linux-image-virtual', 'linux-virtual', 'openssh-client', 'openssh-server', 'openssh-sftp-server', 'systemd', 'systemd-sysv', 'systemd-timesyncd', 'udev']
new snaps: {}
removed snaps: {}
changed snaps: ['lxd']
==== linux-meta: 5.11.0.44.44 => 5.11.0.46.46 ====
====     linux-headers-generic linux-headers-virtual linux-image-virtual linux-virtual
  * Bump ABI 5.11.0-46
  * Bump ABI 5.11.0-45
==== linux-signed: 5.11.0-44.48 => 5.11.0-46.51 ====
====     linux-image-5.11.0-46-generic
  * Master version: 5.11.0-46.51
  * Master version: 5.11.0-45.49
==== openssh: 1:8.4p1-5ubuntu1.1 => 1:8.4p1-5ubuntu1.2 ====
====     openssh-client openssh-server openssh-sftp-server
  * d/p/match-host-certs-w-public-keys.patch: Add patch
    to match host certificates agianst host public keys.
    (LP: #1952421)
==== systemd: 247.3-3ubuntu3.6 => 247.3-3ubuntu3.7 ====
====     libnss-systemd:amd64 libpam-systemd:amd64 libsystemd0:amd64 libudev1:amd64 systemd systemd-sysv systemd-timesyncd udev
  * SECURITY UPDATE: systemd-tmpfiles could be made to crash.
    - d/p/rm-rf-refactor-rm-rf-children-split-out-body-of-directory.patch:
      Backport upstream patch from PR#20173
    - d/p/rm-rf-optionally-fsync-after-removing-directory-tree.patch:
      Backport upstream patch required for CVE-2021-3997 patches
    - d/p/CVE-2021-3997-1.patch: Backport upstream patch to refactor
      rm_rf_children_inner()
    - d/p/CVE-2021-3997-2.patch: Backport upstream patch to refactor
      rm_rf()
    - d/p/CVE-2021-3997-3.patch: Backport upstream patch to loop over
      nested directories instead of using recursion
    - CVE-2021-3997

--
[1] http://cloud-images.ubuntu.com/releases/hirsute/release-20220113/
[2] http://cloud-images.ubuntu.com/releases/hirsute/release-20220106/