CVE 2008-5624
PHP 5 before 5.2.7 does not properly initialize the page_uid and page_gid global variables for use by the SAPI php_getuid function, which allows context-dependent attackers to bypass safe_mode restrictions via variable settings that are intended to be restricted to root, as demonstrated by a setting of /etc for the error_log variable.
See the 
CVE page on Mitre.org
for more details.
