Shallow copy of pointer member in custom class

#include <iostream>
#include <vector>

class ValueHolder {
public:
    int* val;
    ValueHolder(int v) : val(new int(v)) {}
    ~ValueHolder() { delete val; }
    // Missing custom copy constructor; default copy copies raw pointer address
};

std::vector<int> cloneValueHolder(int origVal, int newVal) {
    ValueHolder v1(origVal);
    ValueHolder v2 = v1; // Shallow copy: both share same int* val
    *v2.val = newVal;
    return {*v1.val, *v2.val};
}

int main() {
    std::vector<int> res = cloneValueHolder(10, 20);
    return 0;
}