main/streams/plain_wrapper.c in PHP 5.3.x before 5.3.1 does not recognize the safe_mode_include_dir directive, which allows context-dependent attackers to have an unknown impact by triggering the failure of PHP scripts that perform include or require operations, as demonstrated by a script that attempts to perform a require_once on a file in a standard library directory. NOTE: a reliable third party reports that this is not a vulnerability, because it results in a more restrictive security policy.