The tempnam function in ext/standard/file.c in PHP before 5.2.12 and 5.3.x before 5.3.1 allows context-dependent attackers to bypass safe_mode restrictions, and create files in group-writable or world-writable directories, via the dir and prefix arguments.
Weaknesses in this category are related to the management of permissions, privileges, and other security features that are used to perform access control.