The MITRE CVE dictionary describes this issue as:
The mb_strcut function in Libmbfl 1.1.0, as used in PHP 5.3.x through 5.3.3, allows context-dependent attackers to obtain potentially sensitive information via a large value of the third parameter (aka the length parameter).
Find out more about CVE-2010-4156 from the
MITRE CVE dictionary dictionary and
This issue did not affect the version of php packages as shipped with Red Hat Enterprise Linux 4, 5 or 6. It did affect the PHP 5.3 (php53) package on Red Hat Enterprise Linux 5.