A systemd security update has been released for Ubuntu Linux 20.04 LTS, 21.04, and 21.10.

USN-5226-1: systemd vulnerability

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Ubuntu Security Notice USN-5226-1
January 13, 2022

systemd vulnerability
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A security issue affects these releases of Ubuntu and its derivatives:

- Ubuntu 21.10
- Ubuntu 21.04
- Ubuntu 20.04 LTS

Summary:

systemd-tmpfiles could be made to crash or have other unspecified impacts.

Software Description:
- systemd: system and service manager

Details:

It was discovered that systemd-tmpfiles employed uncontrolled recursion
when removing deeply nested directory hierarchies. A local attacker could
exploit this to cause systemd-tmpfiles to crash or have other unspecified
impacts.

Update instructions:

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

Ubuntu 21.10:
systemd 248.3-1ubuntu8.2

Ubuntu 21.04:
systemd 247.3-3ubuntu3.7

Ubuntu 20.04 LTS:
systemd 245.4-4ubuntu3.15

In general, a standard system update will make all the necessary changes.

References:
  https://ubuntu.com/security/notices/USN-5226-1
CVE-2021-3997

Package Information:
  https://launchpad.net/ubuntu/+source/systemd/248.3-1ubuntu8.2
  https://launchpad.net/ubuntu/+source/systemd/247.3-3ubuntu3.7
  https://launchpad.net/ubuntu/+source/systemd/245.4-4ubuntu3.15