untrusted comment: verify with openbsd-69-base.pub
RWQQsAemppS46EyD0hmyZIlr+Y555Kogy8KpRfojgzvCUJStCm53ebJGPdQ5FwMIshdiJA2vD1yaJ+JJwBsvJwHmrth/pQSRWwA=

OpenBSD 6.9 errata 030, February 21, 2022:

More than 7 nameservers in an IPv6 router advertisement could crash slaacd.

Apply by doing:
    signify -Vep /etc/signify/openbsd-69-base.pub -x 030_slaacd.patch.sig \
        -m - | (cd /usr/src && patch -p0)

And then rebuild and install slaacd:
    cd /usr/src/sbin/slaacd
    make obj
    make
    make install

Index: sbin/slaacd/engine.c
===================================================================
RCS file: /cvs/src/sbin/slaacd/engine.c,v
diff -u -p -u -r1.71 engine.c
--- sbin/slaacd/engine.c	21 Mar 2021 18:25:24 -0000	1.71
+++ sbin/slaacd/engine.c	20 Feb 2022 16:16:20 -0000
@@ -2256,7 +2256,7 @@ gen_rdns_proposal(struct slaacd_iface *i
 	rdns_proposal->rdns_lifetime = ra->rdns_lifetime;
 	LIST_FOREACH(rdns, &ra->rdns_servers, entries) {
 		memcpy(&rdns_proposal->rdns[rdns_proposal->rdns_count++],
-		    &rdns->rdns, sizeof(struct sockaddr_in6));
+		    &rdns->rdns, sizeof(struct in6_addr));
 		if (rdns_proposal->rdns_count == MAX_RDNS_COUNT)
 			break;
 	}