logwatch.pl in Logwatch 7.3.6 allows remote attackers to execute arbitrary commands via shell metacharacters in a log file name, as demonstrated via a crafted username to a Samba server.
The secure script in LogWatch before 2.6-2 allows attackers to prevent LogWatch from detecting malicious activity via certain strings in the secure file that are later used as part of a regular expression, which causes the parser to crash, aka "logwatch log processing regular expression DoS."