Denial-of-service attacks aren't just about external floods: A new US-CERT vulnerability note is a reminder that operating system kernel services can be used to effectively launch a DoS campaign against a system.
Vulnerability Note VU#962459 warns of a vulnerability in Linux kernels versions 4.9 and greater that can allow an attacker to overwhelm a network's resources with low-effort calls. With the right trigger, a Linux system can be forced to make a sequence of kernel calls for every packet – kernel calls that are hugely expensive in terms of system resources. There are limitations on the conditions, but the proof of the vulnerability exists.
Patches for the vulnerability are available for immediate application.