Directory traversal vulnerability in auth.php for PhpBB 1.4.0 through 1.4.4 allows remote attackers to read and include arbitrary files via .. (dot dot) sequences followed by NULL (%00) characters in CGI parameters, as demonstrated using the lang parameter in prefs.php.
Improper Limitation of a Pathname to a Restricted Directory 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.