Just yesterday, Microsoft found a few[0]. There's no shortage of these, but more important is the haphazard way fixes are backported to longterm (e.g. [1]). This reached the point that Google's security advice is 'always follow the latest kernel'[2], except most users and distros simply cannot afford it, so they are stuck with a vulnerable system.
Linux is not unique here. In the longterm, all the typical desktop OSs will need significant structural changes far beyond 'chase vulnerabilities and patch everything all the time'.
True with X11. Fixed in Wayland.