how to define a node in class node in the linked list

i'm trying to define the node in the node class but it gaves me this error on VS Unhandled exception at 0x77477268 (ntdll.dll) in q3.exe: 0xC00000FD: Stack overflow (parameters: 0x00000001, 0x00C02FFC). occurred

class node
{
public:
    node()
    {
        data = 0;
        next = NULL;
    }

    int data;
    node *next = new node();
};

and when I run this function it gives me this error Unhandled exception thrown: read access violation. cur was nullptr. occurred

void list::input(int x)
{
    node *cur = new node();
    node *pr = new node();
    node *temp = new node();
    temp->data = x;
    cur = head;

    if (head == nullptr)
    {
        head = temp;
    }
    else if (x<head->data)
        {
            temp->next = head;
            head = temp;
        }

    else
    {
        while (x > cur->data && cur != nullptr)
        {
            pr = cur;
            cur = cur->next;
        }
        pr->next = temp;
        temp->next = cur;


    }

}