A CWD request has a nonempty parameter giving an encoded pathname. It asks the server to set the name prefix to this pathname, or to another pathname that will have the same effect as this pathname if the filesystem does not change. No such file or directory. Most servers reject CWD requests unless the pathname refers to an accessible directory . Some servers accept all CWD requests, without regard for what directories are actually accessible.
Many servers fail to check for double quotes in the name prefix.
There is no reliable way for the client to compensate for this. Servers are permitted to reject PWD requests with code 550, but high-quality servers will try to accept all PWD requests. A CDUP request asks the server to remove the last slash, and everything following it, from the name prefix. If this produces an empty name prefix, the new name prefix is a single slash. CDUP parameters are prohibited.