diff --git a/include/net/bluetooth/hci_core.h b/include/net/bluetooth/hci_core.h
index e336e9c1dda4..36d727f94ac2 100644
--- a/include/net/bluetooth/hci_core.h
+++ b/include/net/bluetooth/hci_core.h
@@ -294,6 +294,9 @@ struct adv_monitor {
 
 #define HCI_MAX_SHORT_NAME_LENGTH	10
 
+#define HCI_CONN_HANDLE_UNSET		0xffff
+#define HCI_CONN_HANDLE_MAX		0x0eff
+
 /* Min encryption key size to match with SMP */
 #define HCI_MIN_ENC_KEY_SIZE		7
 
diff --git a/net/bluetooth/hci_conn.c b/net/bluetooth/hci_conn.c
index 3bb2b3b6a1c9..84312c836549 100644
--- a/net/bluetooth/hci_conn.c
+++ b/net/bluetooth/hci_conn.c
@@ -691,6 +691,7 @@ struct hci_conn *hci_conn_add(struct hci_dev *hdev, int type, bdaddr_t *dst,
 
 	bacpy(&conn->dst, dst);
 	bacpy(&conn->src, &hdev->bdaddr);
+	conn->handle = HCI_CONN_HANDLE_UNSET;
 	conn->hdev  = hdev;
 	conn->type  = type;
 	conn->role  = role;
diff --git a/net/bluetooth/hci_event.c b/net/bluetooth/hci_event.c
index 519f5906ee98..63b925921c87 100644
--- a/net/bluetooth/hci_event.c
+++ b/net/bluetooth/hci_event.c
@@ -3068,6 +3068,11 @@ static void hci_conn_complete_evt(struct hci_dev *hdev, void *data,
 	struct hci_ev_conn_complete *ev = data;
 	struct hci_conn *conn;
 
+	if (__le16_to_cpu(ev->handle) > HCI_CONN_HANDLE_MAX) {
+		bt_dev_err(hdev, "Ignoring HCI_Connection_Complete for invalid handle");
+		return;
+	}
+
 	bt_dev_dbg(hdev, "status 0x%2.2x", ev->status);
 
 	hci_dev_lock(hdev);
@@ -3106,6 +3111,17 @@ static void hci_conn_complete_evt(struct hci_dev *hdev, void *data,
 		}
 	}
 
+	/* The HCI_Connection_Complete event is only sent once per connection.
+	 * Processing it more than once per connection can corrupt kernel memory.
+	 *
+	 * As the connection handle is set here for the first time, it indicates
+	 * whether the connection is already set up.
+	 */
+	if (conn->handle != HCI_CONN_HANDLE_UNSET) {
+		bt_dev_err(hdev, "Ignoring HCI_Connection_Complete for existing connection");
+		goto unlock;
+	}
+
 	if (!ev->status) {
 		conn->handle = __le16_to_cpu(ev->handle);
 
@@ -4674,6 +4690,11 @@ static void hci_sync_conn_complete_evt(struct hci_dev *hdev, void *data,
 		return;
 	}
 
+	if (__le16_to_cpu(ev->handle) > HCI_CONN_HANDLE_MAX) {
+		bt_dev_err(hdev, "Ignoring HCI_Sync_Conn_Complete for invalid handle");
+		return;
+	}
+
 	bt_dev_dbg(hdev, "status 0x%2.2x", ev->status);
 
 	hci_dev_lock(hdev);
@@ -4697,23 +4718,19 @@ static void hci_sync_conn_complete_evt(struct hci_dev *hdev, void *data,
 			goto unlock;
 	}
 
+	/* The HCI_Synchronous_Connection_Complete event is only sent once per connection.
+	 * Processing it more than once per connection can corrupt kernel memory.
+	 *
+	 * As the connection handle is set here for the first time, it indicates
+	 * whether the connection is already set up.
+	 */
+	if (conn->handle != HCI_CONN_HANDLE_UNSET) {
+		bt_dev_err(hdev, "Ignoring HCI_Sync_Conn_Complete event for existing connection");
+		goto unlock;
+	}
+
 	switch (ev->status) {
 	case 0x00:
-		/* The synchronous connection complete event should only be
-		 * sent once per new connection. Receiving a successful
-		 * complete event when the connection status is already
-		 * BT_CONNECTED means that the device is misbehaving and sent
-		 * multiple complete event packets for the same new connection.
-		 *
-		 * Registering the device more than once can corrupt kernel
-		 * memory, hence upon detecting this invalid event, we report
-		 * an error and ignore the packet.
-		 */
-		if (conn->state == BT_CONNECTED) {
-			bt_dev_err(hdev, "Ignoring connect complete event for existing connection");
-			goto unlock;
-		}
-
 		conn->handle = __le16_to_cpu(ev->handle);
 		conn->state  = BT_CONNECTED;
 		conn->type   = ev->link_type;
@@ -5509,6 +5526,11 @@ static void le_conn_complete_evt(struct hci_dev *hdev, u8 status,
 	struct smp_irk *irk;
 	u8 addr_type;
 
+	if (handle > HCI_CONN_HANDLE_MAX) {
+		bt_dev_err(hdev, "Ignoring HCI_LE_Connection_Complete for invalid handle");
+		return;
+	}
+
 	hci_dev_lock(hdev);
 
 	/* All controllers implicitly stop advertising in the event of a
@@ -5550,6 +5572,17 @@ static void le_conn_complete_evt(struct hci_dev *hdev, u8 status,
 		cancel_delayed_work(&conn->le_conn_timeout);
 	}
 
+	/* The HCI_LE_Connection_Complete event is only sent once per connection.
+	 * Processing it more than once per connection can corrupt kernel memory.
+	 *
+	 * As the connection handle is set here for the first time, it indicates
+	 * whether the connection is already set up.
+	 */
+	if (conn->handle != HCI_CONN_HANDLE_UNSET) {
+		bt_dev_err(hdev, "Ignoring HCI_Connection_Complete for existing connection");
+		goto unlock;
+	}
+
 	le_conn_update_addr(conn, bdaddr, bdaddr_type, local_rpa);
 
 	/* Lookup the identity address from the stored connection