hi,

in php 5.3.1 security changelog, we can read, that safe_mode bypass in tempnam() has been already fixed. But safe_mode in 5.3 line is deprecated. We can understand security fix for open_basedir bypass, but not for safe_mode in 5.3.
Annoying is the fact, that exploit for bypass open_basedir or safe_mode in php 5.3.1 is avaliable in

http://securityreason.com/achievement_exploitalert/14 

we can use symlink trick like in

http://securityreason.com/achievement_securityalert/70 

The issue has been reported to PHP, but did not obtain a meaningful response.
Very similar issue has been reproted in October 2006 by Stefan Esser (SREASON:1692)

http://securityreason.com/securityalert/1692 

This issue has been fixed.
Small difference, with this is that we need create fake directories structure.

best,
Maksymilian Arciemowicz
cxibTAsecurityreasonTODcom