main/php_open_temporary_file.c in PHP before 5.5.28 and 5.6.x before 5.6.12 does not ensure thread safety, which allows remote attackers to cause a denial of service (race condition and heap memory corruption) by leveraging an application that performs many temporary-file accesses. http://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2015-8878
