An issue was discovered in certain Apple products. macOS before 10.13.1 is affected. The issue involves the "CFNetwork" component. It allows attackers to execute arbitrary code in a privileged context or cause a denial of service (memory corruption) via a crafted app.
https://support.apple.com/HT208331
https://support.apple.com/HT208221
http://www.securitytracker.com/id/1039966
http://www.securitytracker.com/id/1039953