diff --git a/sys/netproto/802_11/wlan_wep/ieee80211_crypto_wep.c b/sys/netproto/802_11/wlan_wep/ieee80211_crypto_wep.c
--- a/sys/netproto/802_11/wlan_wep/ieee80211_crypto_wep.c
+++ b/sys/netproto/802_11/wlan_wep/ieee80211_crypto_wep.c
@@ -122,7 +122,7 @@
 static int
 wep_setkey(struct ieee80211_key *k)
 {
-	return k->wk_keylen >= 40/NBBY;
+	return (k->wk_keylen >= 40/NBBY && k->wk_keylen <= IEEE80211_KEYBUF_SIZE);
 }
 
 static void