ascii_load_sockaddr in smtpd in OpenBSD before 7.1 errata 024 and 7.2 before errata 020, and OpenSMTPD Portable before 7.0.0-portable commit f748277, can abort upon a connection from a local, scoped IPv6 address.
https://security.netapp.com/advisory/ntap-20230526-0006/
https://github.com/openbsd/src/commit/f748277ed1fc7065ae8998d61ed78b9ab1e55fae
https://github.com/OpenSMTPD/OpenSMTPD/commit/41d0eae481f538956b1f1fbadfb535043454061f
https://ftp.openbsd.org/pub/OpenBSD/patches/7.2/common/020_smtpd.patch.sig
https://ftp.openbsd.org/pub/OpenBSD/patches/7.1/common/024_smtpd.patch.sig
https://cvsweb.openbsd.org/cgi-bin/cvsweb/src/usr.sbin/smtpd/envelope.c.diff?r1=1.50&r2=1.51&f=h
https://cvsweb.openbsd.org/cgi-bin/cvsweb/src/usr.sbin/smtpd/envelope.c.diff?r1=1.50&r2=1.50.4.1&f=h
https://cvsweb.openbsd.org/cgi-bin/cvsweb/src/usr.sbin/smtpd/envelope.c.diff?r1=1.49&r2=1.49.4.1&f=h