The session deserializer in PHP before 5.4.45, 5.5.x before 5.5.29, and 5.6.x before 5.6.13 mishandles multiple php_var_unserialize calls, which allow remote attackers to execute arbitrary code or cause a denial of service (use-after-free) via crafted session content.<a href=http://cwe.mitre.org/data/definitions/416.html>CWE-416: Use After Free</a> http://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2015-6835