In Apache SpamAssassin before 3.4.3, nefarious CF files can be configured to run system commands without any output or errors. With this, exploits can be injected in a number of scenarios. In addition to upgrading to SA 3.4.3, we recommend that users should only use update channels or 3rd party .cf files from trusted places.
https://www.debian.org/security/2019/dsa-4584
https://usn.ubuntu.com/4237-2/
https://usn.ubuntu.com/4237-1/
https://svn.apache.org/repos/asf/spamassassin/branches/3.4/build/announcements/3.4.3.txt
https://seclists.org/oss-sec/2019/q4/154
https://seclists.org/bugtraq/2019/Dec/27
https://lists.debian.org/debian-lts-announce/2019/12/msg00019.html
https://bz.apache.org/SpamAssassin/show_bug.cgi?id=7647
http://www.openwall.com/lists/oss-security/2020/01/30/3
http://www.openwall.com/lists/oss-security/2020/01/30/2
http://www.openwall.com/lists/oss-security/2019/12/12/1
http://lists.opensuse.org/opensuse-security-announce/2020-04/msg00003.html