Index: sbin/ipfw/ipv6.c
===================================================================
--- sbin/ipfw/ipv6.c
+++ sbin/ipfw/ipv6.c
@@ -339,6 +339,7 @@
 {
 	int len = 0;
 	struct in6_addr *d = &(cmd->addr6);
+	char *oav;
 	/*
 	 * Needed for multiple address.
 	 * Note d[1] points to struct in6_add r mask6 of cmd
@@ -365,7 +366,7 @@
 		return (1);
 	}
 
-	av = strdup(av);
+	oav = av = strdup(av);
 	while (av) {
 		/*
 		 * After the address we can have '/' indicating a mask,
@@ -411,6 +412,7 @@
 
 		APPLY_MASK(d, &d[1])   /* mask base address with mask */
 
+		/* Changes the value of av */
 		av = q;
 
 		/* Check this entry */
@@ -446,7 +448,7 @@
 	if (len + 1 > F_LEN_MASK)
 		errx(EX_DATAERR, "address list too long");
 	cmd->o.len |= len+1;
-	free(av);
+	free(oav);
 	return (1);
 }