static CURLcode smtp_state_command_resp(struct connectdata *conn, int smtpcode,
                                        smtpstate instate)
{
  CURLcode result = CURLE_OK;
  struct Curl_easy *data = conn->data;
  struct SMTP *smtp = data->req.protop;
  char *line = data->state.buffer;
  size_t len = strlen(line);

  (void)instate; /* no use for this yet */

  if((smtp->rcpt && smtpcode/100 != 2 && smtpcode != 553 && smtpcode != 1) ||
     (!smtp->rcpt && smtpcode/100 != 2 && smtpcode != 1)) {
    failf(data, "Command failed: %d", smtpcode);
    result = CURLE_RECV_ERROR;
  }
  else {
    /* Temporarily add the LF character back and send as body to the client */
    if(!data->set.opt_no_body) {
      line[len] = '\n';
      result = Curl_client_write(conn, CLIENTWRITE_BODY, line, len + 1);
      line[len] = '\0';
    }

    if(smtpcode != 1) {
      if(smtp->rcpt) {
        smtp->rcpt = smtp->rcpt->next;

        if(smtp->rcpt) {
          /* Send the next command */
          result = smtp_perform_command(conn);
        }
        else
          /* End of DO phase */
          state(conn, SMTP_STOP);
      }
      else
        /* End of DO phase */
        state(conn, SMTP_STOP);
    }
  }

  return result;
}

The product performs operations on a memory buffer, but it reads from or writes to a memory location outside the buffer's intended boundary. This may result in read or write operations on unexpected memory locations that could be linked to other variables, data structures, or internal program data.