The MITRE CVE dictionary describes this issue as:
The openssl_x509_parse function in openssl.c in the OpenSSL module in PHP before 5.4.18 and 5.5.x before 5.5.2 does not properly handle a '\\0' character in a domain name in the Subject Alternative Name field of an X.509 certificate, which allows man-in-the-middle attackers to spoof arbitrary SSL servers via a crafted certificate issued by a legitimate Certification Authority, a related issue to CVE-2009-2408.
Find out more about CVE-2013-4248 from the
MITRE CVE dictionary dictionary and
This issue does not affect the version of php as shipped with Red Hat Enterprise Linux 5 or the version of php54 as shipped with Red Hat Software Collections 1.