In GNOME evolution-data-server before 3.35.91, a malicious server can crash the mail client with a NULL pointer dereference by sending an invalid (e.g., minimal) CAPABILITY line on a connection attempt. This is related to imapx_free_capability and imapx_connect_to_server.
gitlab.gnome.org/GNOME/evolution-data-server/-/commit/2cc39592b532cf0dc994fd3694b8e6bf924c9ab5
gitlab.gnome.org/GNOME/evolution-data-server/-/commit/627c3cdbfd077e59aa288c85ff8272950577f1d7
gitlab.gnome.org/GNOME/evolution-data-server/-/issues/189
lists.debian.org/debian-lts-announce/2020/08/msg00005.html