diff --git a/sbin/slaacd/engine.c b/sbin/slaacd/engine.c
index 8f1bd038533..1ab6fb38f33 100644
--- a/sbin/slaacd/engine.c
+++ b/sbin/slaacd/engine.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: engine.c,v 1.99 2024/11/21 13:35:20 claudio Exp $	*/
+/*	$OpenBSD: engine.c,v 1.100 2026/04/12 23:57:31 deraadt Exp $	*/
 
 /*
  * Copyright (c) 2017 Florian Obser <florian@openbsd.org>
@@ -1474,6 +1474,8 @@ parse_ra(struct slaacd_iface *iface, struct imsg_ra *ra)
 		struct in6_addr *in6;
 		int i;
 
+		if (nd_opt_hdr->nd_opt_len == 0)
+			goto err;
 		len -= sizeof(struct nd_opt_hdr);
 		p += sizeof(struct nd_opt_hdr);
 
@@ -1760,6 +1762,8 @@ debug_log_ra(struct imsg_ra *ra)
 		struct in6_addr *in6;
 		int i;
 
+		if (nd_opt_hdr->nd_opt_len == 0)
+			return;
 		len -= sizeof(struct nd_opt_hdr);
 		p += sizeof(struct nd_opt_hdr);
 		if (nd_opt_hdr->nd_opt_len * 8 - 2 > len) {
diff --git a/usr.sbin/rad/engine.c b/usr.sbin/rad/engine.c
index 98fdd105cfc..f46d5c83bbb 100644
--- a/usr.sbin/rad/engine.c
+++ b/usr.sbin/rad/engine.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: engine.c,v 1.29 2025/04/27 16:23:04 florian Exp $	*/
+/*	$OpenBSD: engine.c,v 1.30 2026/04/12 23:57:27 deraadt Exp $	*/
 
 /*
  * Copyright (c) 2018 Florian Obser <florian@openbsd.org>
@@ -541,6 +541,8 @@ parse_rs(struct imsg_ra_rs *rs)
 	while ((size_t)len >= sizeof(struct nd_opt_hdr)) {
 		struct nd_opt_hdr *nd_opt_hdr = (struct nd_opt_hdr *)p;
 
+		if (nd_opt_hdr->nd_opt_len == 0)
+			return;
 		len -= sizeof(struct nd_opt_hdr);
 		p += sizeof(struct nd_opt_hdr);