untrusted comment: verify with openbsd-68-base.pub
RWQZj25CSG5R2h7LFmAu1l2QlTNpkZM5O9FpvyBh29lTUHqg5lv+cy1JX6sjnHI4hTCxfZyw13PgXDKpfHyHFjSAXFf4liknwQU=

OpenBSD 6.8 errata 012, January 13, 2021:

Use of bpf(4) on a carp interface could result in a use after free
error.

Apply by doing:
   signify -Vep /etc/signify/openbsd-68-base.pub -x 012_carp.patch.sig \
       -m - | (cd /usr/src && patch -p0)

And then rebuild and install a new kernel:
   KK=`sysctl -n kern.osversion | cut -d# -f1`
   cd /usr/src/sys/arch/`machine`/compile/$KK
   make obj
   make config
   make
   make install

Index: sys/netinet/ip_carp.c
===================================================================
RCS file: /cvs/src/sys/netinet/ip_carp.c,v
retrieving revision 1.349
diff -u -p -r1.349 ip_carp.c
--- sys/netinet/ip_carp.c       28 Jul 2020 16:44:34 -0000      1.349
+++ sys/netinet/ip_carp.c       8 Jan 2021 13:38:29 -0000
@@ -2282,10 +2282,8 @@ carp_transmit(struct carp_softc *sc, str
#if NBPFILTER > 0
       {
               caddr_t if_bpf = ifp->if_bpf;
-               if (if_bpf) {
-                       if (bpf_mtap_ether(if_bpf, m, BPF_DIRECTION_OUT))
-                               m_freem(m);
-               }
+               if (if_bpf)
+                       bpf_mtap_ether(if_bpf, m, BPF_DIRECTION_OUT);
       }
#endif /* NBPFILTER > 0 */