Wi-Fi in Apple iOS before 10.3.1 does not prevent CVE-2017-6956 stack buffer overflow exploitation via a crafted access point. NOTE: because an operating system could potentially isolate itself from CVE-2017-6956 exploitation without patching Broadcom firmware functions, there is a separate CVE ID for the operating-system behavior.
http://seclists.org/fulldisclosure/2019/May/24
https://googleprojectzero.blogspot.com/2017/04/over-air-exploiting-broadcoms-wi-fi_4.html
https://seclists.org/bugtraq/2019/May/30
https://support.apple.com/HT207688
https://support.apple.com/kb/HT210121