The Calendar Base (cal) extension before 1.5.9 and 1.6.x before 1.6.1 for TYPO3 allows remote attackers to cause a denial of service (resource consumption) via vectors related to the PHP PCRE library.
http://www.securityfocus.com/bid/70645
http://www.openwall.com/lists/oss-security/2014/10/17/11
http://typo3.org/teams/security/security-bulletins/typo3-extensions/typo3-ext-sa-2014-013/