In the IMAP Server in Dovecot 2.3.3 through 2.3.5.2, the submission-login component crashes if AUTH PLAIN is attempted over a TLS secured channel with an unacceptable authentication message.
lists.opensuse.org/opensuse-security-announce/2019-10/msg00024.html
lists.opensuse.org/opensuse-security-announce/2019-10/msg00026.html
lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/4XLI55NGRDTGMVOPYFCPPFNPA5VKYSSY/
lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/QHFZ5OWRIZGIWZJ5PTNVWWZNLLNH4XYS/
www.dovecot.org/download.html
www.dovecot.org/security.html