A memory corruption issue existed in the handling of IPv6 packets. This issue was addressed with improved memory management. This issue is fixed in macOS Catalina 10.15, tvOS 13, macOS Catalina 10.15.1, Security Update 2019-001, and Security Update 2019-006, watchOS 6, iOS 13. A malicious application may be able to determine kernel memory layout.
https://support.apple.com/en-us/HT210722
https://support.apple.com/en-us/HT210634
https://support.apple.com/en-us/HT210607