=== What is the potential impact?

Accessing a dangling reference or pointer causes undefined behavior.
This means the compiler is not bound by the language standard anymore and your program has no meaning assigned to it.

Practically this has a wide range of effects.
In many cases, the access works by accident and succeeds at writing or reading a value.
However, it can start misbehaving at any time.
If compilation flags, compiler, platform, or runtime environment change,
the same code can crash the application, corrupt memory, or leak a secret.
