 static int nntp_hcache_namer(const char *path, char *dest, size_t destlen)
 {
  return snprintf(dest, destlen, "%s.hcache", path);
 }

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.