There's the following assert in ClassLoader::update_module_path_entry_list() for making sure a module path exists.

    assert(ret == 0, "module path must exist");

For a very long module path with length > 2K, the path exists but os::stat() returns ENAMETOOLONG error on linux.
int os::stat(const char *path, struct stat *sbuf) {
  char pathbuf[MAX_PATH];
  if (strlen(path) > MAX_PATH - 1) {
    errno = ENAMETOOLONG; <<<<< here
    return -1;
  }
  os::native_path(strcpy(pathbuf, path));
  return ::stat(pathbuf, sbuf);
}

The assert should be replaced with an error message and the CDS dumping should be aborted.