The wasm vm has to parse, validate, and compile untrusted input. It also exposes host calls. Those are all potential attack vectors. That’s at least roughly 50K LOC.

>It also exposes host calls.

Only if you grant explicit access to them. What usually happens is that there is a vendor provided API that only gives you access to exactly what you need which is significantly less powerful than a complete linux process that can write to files, spawn background threads, etc all by default.

Yes you can block access to these things but you're going to miss something at some point.

In seccomp the only syscalls available are read, write, exit, and sigreturn. There is nothing to miss