MySQL 5.0.88, and possibly other versions and platforms, allows local users to bypass certain privilege checks by calling CREATE TABLE on a MyISAM table with modified (1) DATA DIRECTORY or (2) INDEX DIRECTORY arguments that are originally associated with pathnames without symlinks, and that can point to tables created at a future time at which a pathname is modified to contain a symlink to a subdirectory of the MySQL data home directory, related to incorrect calculation of the mysql_unpacked_real_data_home value.  NOTE: this vulnerability exists because of a CVE-2009-4030 regression, which was not omitted in other packages and versions such as MySQL 5.0.95 in Red Hat Enterprise Linux 6.