bool RealPath(const FilePath& path, FilePath* real_path) {
  base::ThreadRestrictions::AssertIOAllowed();  // For realpath().
  FilePath::CharType buf[PATH_MAX];
  if (!realpath(path.value().c_str(), buf))
    return false;

  *real_path = FilePath(buf);
  return true;
}

The product uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the product does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory.