In PHP through 5.6.33, 7.0.x before 7.0.28, 7.1.x through 7.1.14, and 7.2.x through 7.2.2, there is a stack-based buffer under-read while parsing an HTTP response in the phpstreamurlwraphttpex function in ext/standard/httpfopen_wrapper.c. This subsequently results in copying a large string.