An Apache Log4j 2 security update has been released for Ubuntu Linux 20.04 LTS, 21.04, and 21.10.

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Ubuntu Security Notice USN-5203-1
December 19, 2021

apache-log4j2 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:

Apache Log4j 2 could be made to crash if it received specially crafted
input.

Software Description:
- apache-log4j2: Apache Log4j - Logging Framework for Java

Details:

Hideki Okamoto and Guy Lederfein discovered that Apache Log4j 2 did not
protect against infinite recursion in lookup evaluation. A remote attacker
could possibly use this issue to cause Apache Log4j 2 to crash, leading to
a denial of service.

Update instructions:

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

Ubuntu 21.10:
liblog4j2-java 2.17.0-0.21.10.1

Ubuntu 21.04:
liblog4j2-java 2.17.0-0.21.04.1

Ubuntu 20.04 LTS:
liblog4j2-java 2.17.0-0.20.04.1

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

References:
  https://ubuntu.com/security/notices/USN-5203-1
CVE-2021-45105

Package Information:
  https://launchpad.net/ubuntu/+source/apache-log4j2/2.17.0-0.21.10.1
  https://launchpad.net/ubuntu/+source/apache-log4j2/2.17.0-0.21.04.1
  https://launchpad.net/ubuntu/+source/apache-log4j2/2.17.0-0.20.04.1