This isn't theoretical, I've seen it with HTTP, HTML and elsewhere. Any time two pieces of software disagree on how to parse a chunk of data, especially if one

This isn't theoretical, I've seen it with HTTP, HTML and elsewhere. Any time two pieces of software disagree on how to parse a chunk of data, especially if one of them is supposed to be doing some sort of security check, you should expect to find a vulnerability lurking. I don't know if there's a name for this class of problem. I'd be interested to know.