It’s not a joke, people saying otherwise did not understand the paper. The significance is debatable, it’s mostly a kind of collective facepalm for theoretical computer scientists.

The CVE is a joke in the sense that you don’t really need a CVE for a universal Turing machine, as they are quite literally only academic.

i dont know if he says exactly that by i do say exactly that

paper is essentially saying that by using simplest machine possible

we prove it does not provide layers of security abstractions which were invented and deployed in last 40+ years to computers

so thats like getting CVE for turning off ASLR, AppARMOR SElinux etc in linux kernel.

As far as I can tell, yes, it is.

Showing a universal Turing machine is a proof of the fact that when you write stuff like the smn theorem or anything that uses universal functions you aren't writing nonsense.

There is no "contract" between the universal machine and the hypothetical user. One could certainly ensure that, say, the input TM is properly formatted, or that "the runtime" will only use a certain set of cells, and so on. The difficulties and problems one would find in trying to do so are the same one would face when writing an operating system and a compiler.