Might want to integrate an existing C++ code base into a server without developing an API or IPC in between the two. The security issues would be similar in either case and this would be much quicker to develop.
Or perhaps you might want to use a belt sander to refinish your table without removing the tablecloth from the table first. Not all the things one “might want to do” are good ideas, even if there’s a wikihow on best ways to do them.
C++ is a great language but it’s a very hard language to wield correctly. The odds there is an exploitable buffer overflow or injection attack buried deep in some part of the code are simply too high compared to memory managed languages with standard libraries designed from the ground up for web-facing applications.
There is almost literally no chance that this is the case. The amount of pointless boilerplate code that you'd have to write would be many, many, many times in excess of a thin API layer.