Use-after-free vulnerability in the process_nested_data function in ext/standard/var_unserializer.re in PHP before 5.4.39, 5.5.x before 5.5.23, and 5.6.x before 5.6.7 allows remote attackers to execute arbitrary code via a crafted unserialize call that leverages use of the unset function within an __wakeup function, a related issue to CVE-2015-0231.