An apache-log4j2 security update has been released for Debian GNU/Linux 9 LTS to address several security vulnerabilities.

DLA 2852-1: apache-log4j2 security update

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Debian LTS Advisory DLA-2852-1 debian-lts@lists.debian.org
  https://www.debian.org/lts/security/ Markus Koschany
December 26, 2021   https://wiki.debian.org/LTS
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Package : apache-log4j2
Version : 2.12.3-0+deb9u1
CVE ID : CVE-2020-9488 CVE-2021-45105
Debian Bug : 959450 1001891

Several security vulnerabilities were found in Apache Log4j2, a Logging
Framework for Java, which could lead to a denial of service or information
disclosure.

CVE-2020-9488

Improper validation of certificate with host mismatch in Apache Log4j SMTP
appender. This could allow an SMTPS connection to be intercepted by a
man-in-the-middle attack which could leak any log messages sent through
that appender.

CVE-2021-45105

Apache Log4j2 did not protect from uncontrolled recursion from
self-referential lookups. This allows an attacker with control over Thread
Context Map data to cause a denial of service when a crafted string is
interpreted.

For Debian 9 stretch, these problems have been fixed in version
2.12.3-0+deb9u1.

We recommend that you upgrade your apache-log4j2 packages.

For the detailed security status of apache-log4j2 please refer to
its security tracker page at:
  https://security-tracker.debian.org/tracker/apache-log4j2

Further information about Debian LTS security advisories, how to apply
these updates to your system and frequently asked questions can be
found at:   https://wiki.debian.org/LTS