c++ - How serious is the new/delete operator mismatch error?

Question

I have discovered the classic new/delete mismatch error in our codebase as follows:

char *foo = new char[10];

// do something

delete foo; // instead of delete[] foo;

Just how serious is this? Does it cause a memory leak or error? What are the consequences. We have some memory issues, but this doesn't seem serious enough to explain all our symptoms (heap corruption etc)

EDIT: extra questions for clarity
Does it just free the first member of the array? or
Does it make the system lose track of the array? or
Corrupt memory is some way?

Answer 1

It's undefined behavior serious (it could work, it could crash, it could do something else).