untrusted comment: verify with openbsd-67-base.pub
RWRmkIA877Io3qdkPFhXqkFINTzcQsdYbEc5sDsN1X3gIhi14ysuB9QkAG9wWNUK3pxa9sWBxrVyqpJEA0vURn3HXh93m0uuMQo=

OpenBSD 6.7 errata 036, March 4, 2021:

Double free in ssh-agent(1)

Apply by doing:
    signify -Vep /etc/signify/openbsd-67-base.pub -x 036_sshagent.patch.sig \
        -m - | (cd /usr/src && patch -p0)

And then rebuild and install ssh (as well as ssh-agent)
    cd /usr/src/usr.bin/ssh
    make obj
    make clean
    make
    make install

Index: usr.bin/ssh/ssh-agent.c
===================================================================
RCS file: /cvs/src/usr.bin/ssh/ssh-agent.c,v
diff -u -p -u -r1.257 ssh-agent.c
--- usr.bin/ssh/ssh-agent.c	6 Mar 2020 18:28:27 -0000	1.257
+++ usr.bin/ssh/ssh-agent.c	3 Mar 2021 15:32:14 -0000
@@ -482,6 +482,7 @@ process_add_identity(SocketEntry *e)
 				goto err;
 			}
 			free(ext_name);
+			ext_name = NULL;
 			break;
 		default:
 			error("%s: Unknown constraint %d", __func__, ctype);