Comment 1 for bug 1406840

I can confirm this with Vivid's sshfs version 2.5-1ubuntu1. Well, except for the detail that the problem didn't appear to be with passwords longer than 64 characters, but rather with passwords 64 characters (inclusive) or longer.

Not sure whatever to categorize it as a bug or not, given that the program strictly speaking is behaving as intended, even if I agree that it appear to be arbitrary.

My suggestion is to bring the case up with upstream. According to http://fuse.sourceforge.net/sshfs.html the suggested method is to send an e-mail to <email address hidden>.