Georgi Guninski security advisory #65, 2004 – Qmail version 1.03 is susceptible to a couple attacks. A crash in qmail-smtpd occurs with a long SMTP session. The crash is not global, it affects only the current SMTP session. It is also possible to trigger a segmentation violation (SEGV) from the network.
You can download this advisory from the following link: https://packetstormsecurity.com/files/download/32526/qmailcrash.html
Source: https://packetstormsecurity.com/files/32526/qmailcrash.html.html