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.