I have seen that in the C or C++ abstract machine, the mere act of forming a point to an invalid point in memory is undefined behavior.

For example

int* arr = new int[10];
int* last = arr + 9;  // last element
int* end = arr + 10; // past last element, still ok according to the rules
int* another = arr + 11;  // invalid, UB, supposedly, the rest of the program can be invalid

Now suppose, this other code

int* arr;  // arr can be invalid already here, UB?
int* another = arr;  // forming a pointer to possibly invalid memory, UB?

How is assigning an uninitialized pointer different from forming an invalid pointer by an operation? is it as bad?