The MITRE CVE dictionary describes this issue as:
Stack-based buffer overflow in the socket_connect function in ext/sockets/sockets.c in PHP 5.3.3 through 5.3.6 might allow context-dependent attackers to execute arbitrary code via a long pathname for a UNIX socket.
Find out more about CVE-2011-1938 from the
MITRE CVE dictionary dictionary and
Not vulnerable. This issue did not affect the versions of php as shipped with Red Hat Enterprise Linux 4 and 5. It has been addressed in Red Hat Enterprise Linux 5 (php53) and 6 (php).