In PHP before 5.6.31, 7.x before 7.0.21, and 7.1.x before 7.1.7, a stack-based buffer overflow in the zend_ini_do_op() function in Zend/zend_ini_parser.c could cause a denial of service or potentially allow executing code. NOTE: this is only relevant for PHP applications that accept untrusted input (instead of the system's php.ini file) for the parse_ini_string or parse_ini_file function, e.g., a web application for syntax validation of php.ini directives.