It was discovered that Dovecot before versions 2.2.36.1 and 2.3.4.1 incorrectly handled client certificates. A remote attacker in possession of a valid certificate with an empty username field could possibly use this issue to impersonate other users.
lists.opensuse.org/opensuse-security-announce/2019-04/msg00067.html
access.redhat.com/errata/RHSA-2019:3467
bugzilla.redhat.com/show_bug.cgi?id=CVE-2019-3814
lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/4XLI55NGRDTGMVOPYFCPPFNPA5VKYSSY/
lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/QHFZ5OWRIZGIWZJ5PTNVWWZNLLNH4XYS/
security.gentoo.org/glsa/201904-19
www.dovecot.org/list/dovecot/2019-February/114575.html