diff --git a/net/ethtool/cmis_fw_update.c b/net/ethtool/cmis_fw_update.c
index 16190c97e1f7..291d04d2776a 100644
--- a/net/ethtool/cmis_fw_update.c
+++ b/net/ethtool/cmis_fw_update.c
@@ -130,6 +130,14 @@ cmis_fw_update_start_download(struct ethtool_cmis_cdb *cdb,
 	u8 lpl_len;
 	int err;
 
+	if (fw_update->fw->size < vendor_data_size) {
+		ethnl_module_fw_flash_ntf_err(fw_update->dev,
+					      &fw_update->ntf_params,
+					      "Firmware image too small for module's start payload",
+					      NULL);
+		return -EINVAL;
+	}
+
 	pl.image_size = cpu_to_be32(fw_update->fw->size);
 	memcpy(pl.vendor_data, fw_update->fw->data, vendor_data_size);