The simplest instance of CVD is when there are only two parties involved: the finder of the vulnerability and the vendor who can fix the software. In this case, many of the complexities that arise in multiparty situations do not come into play.
That is not to say that two-party CVD is always straightforward or easy. It can still be difficult for the finder of a vulnerability to make contact with the vendor. It can sometimes be difficult for the vendor to work with the finder toward a resolution.
Personalities, attitudes, expectations, assumptions, and egos all play a part in the success or failure of even two-party CVD.