According to krackattacks.com, An attacker within range of a victim can serious weakness of WPA2 using key reinstallation attacks (KRACKs). Attackers can use this attack technique to read information that was previously assumed to be safely encrypted. This can be abused to steal sensitive information such as credit card numbers, passwords, chat messages, emails, photos, and so on. The attack works against all modern protected Wi-Fi networks. Depending on the network configuration, it is also possible to inject and manipulate data.
If your device supports Wi-Fi, it is most likely affected. Google is expected to fix this vulnerability with its November Security patch, which will be available next month for Nexus and Pixel devices. Until then if your device is unlocked and have custom recovery, you can install the latest LineageOS 14.1 build.
LineageOS 15 based on Android Oreo is coming soon: "While the cm-14.1 branch development hasn’t stopped, we’re also working on the next LineageOS version (15.0), based on the latest Android 8.0. We will refrain from giving any ETA, just patiently wait until the new branch is ready for release-time. - Team Lineage OS"