The get_icu_value_internal function in ext/intl/locale/locale_methods.c in PHP before 5.5.36, 5.6.x before 5.6.22, and 7.x before 7.0.7 does not ensure the presence of a '\0' character, which allows remote attackers to cause a denial of service (out-of-bounds read) or possibly have unspecified other impact via a crafted locale_get_primary_language call.
http://php.net/ChangeLog-5.php
http://php.net/ChangeLog-7.php
http://rhn.redhat.com/errata/RHSA-2016-2750.html
https://bugs.php.net/bug.php?id=72241
https://github.com/php/php-src/commit/97eff7eb57fc2320c267a949cffd622c38712484?w=1
https://h20566.www2.hpe.com/portal/site/hpsc/public/kb/docDisplay?docId=emr_na-c05240731