CVE 2015-0273
Multiple use-after-free vulnerabilities in ext/date/php_date.c in PHP before 5.4.38, 5.5.x before 5.5.22, and 5.6.x before 5.6.6 allow remote attackers to execute arbitrary code via crafted serialized input containing a (1) R or (2) r type specifier in (a) DateTimeZone data handled by the php_date_
See the 
CVE page on Mitre.org
for more details.
