diff --git a/drivers/isdn/hardware/mISDN/hfcsusb.c b/drivers/isdn/hardware/mISDN/hfcsusb.c
index 4c99739b937e..79081ca1e7b0 100644
--- a/drivers/isdn/hardware/mISDN/hfcsusb.c
+++ b/drivers/isdn/hardware/mISDN/hfcsusb.c
@@ -1955,6 +1955,9 @@ hfcsusb_probe(struct usb_interface *intf, const struct usb_device_id *id)
 
 				/* get endpoint base */
 				idx = ((ep_addr & 0x7f) - 1) * 2;
+				if (idx > 15) {
+					return -EIO;
+				}
 				if (ep_addr & 0x80)
 					idx++;
 				attr = ep->desc.bmAttributes;