The sapi_header_op function in main/SAPI.c in PHP before 5.3.11 and 5.4.x before 5.4.0RC2 does not check for %0D sequences (aka carriage return characters), which allows remote attackers to bypass an HTTP response-splitting protection mechanism via a crafted URL, related to improper interaction between the PHP header function and certain browsers, as demonstrated by Internet Explorer and Google Chrome.
https://bugs.php.net/bug.php?id=60227
http://www.ubuntu.com/usn/USN-1569-1
http://www.securitytracker.com/id?1027463
http://security-tracker.debian.org/tracker/CVE-2011-1398
http://secunia.com/advisories/55078
http://rhn.redhat.com/errata/RHSA-2013-1307.html
http://openwall.com/lists/oss-security/2012/09/05/15
http://openwall.com/lists/oss-security/2012/08/29/5
http://lists.opensuse.org/opensuse-security-announce/2013-08/msg00006.html