An issue was discovered in certain Apple products. iOS before 10.2 is affected. macOS before 10.12.2 is affected. watchOS before 3.1.3 is affected. The issue involves the "Security" component, which allows man-in-the-middle attackers to cause a denial of service (application crash) via vectors related to OCSP responder URLs.
https://support.apple.com/HT207487
https://support.apple.com/HT207423
https://support.apple.com/HT207422