sendmessage.cgi in W3Mail 1.0.2, and possibly other CGI programs, allows remote attackers to execute arbitrary commands via shell metacharacters in any field of the 'Compose Message' page.
https://exchange.xforce.ibmcloud.com/vulnerabilities/7230
https://euvd.enisa.europa.eu/vulnerability/EUVD-2001-1081
http://www.w3mail.org/ChangeLog