In GNOME Balsa before 2.6.0, a malicious server operator or man in the middle can trigger a NULL pointer dereference and client crash by sending a PREAUTH response to imap_mbox_connect in libbalsa/imap/imap-handle.c.
https://gitlab.gnome.org/GNOME/balsa/-/issues/23
https://gitlab.gnome.org/GNOME/balsa/-/commit/4e245d758e1c826a01080d40c22ca8706f0339e5
http://lists.opensuse.org/opensuse-security-announce/2020-08/msg00045.html
http://lists.opensuse.org/opensuse-security-announce/2020-08/msg00035.html