Not impossible. Harder.

That distinction matters.

Because every time people talk about Rust, the conversation eventually becomes a little too absolute. "Rust prevents memory bugs." "Rust is safe." "Rust fixes what C and C++ got wrong." And to be fair, there is a lot of truth in that. Rust does raise the floor. It does prevent entire classes of bugs that have haunted software for decades.

AI Assisted Rust Security : https://tobiweissmann.gumroad.com/l/rhsdn

But software engineering has a way of punishing absolute thinking.

This week, a small but important story came out of the Rust ecosystem: the Rust Foundation has apparently been using Claude Mythos to review the standard library for security issues, and a couple of minor unsoundness bugs have now been made public while more severe ones remain under embargo.

And honestly, I think this is one of those moments people will look back on later and say: that was the beginning of a different era.

Not because Rust "failed."

Not because AI is now replacing security engineers.

But because the shape of security work is changing right in front of us.

The public issues themselves are technical, but the bigger meaning is easy to understand.

One involved CString::clone_into(), where a very specific allocation-failure path could lead to broken invariants and potentially an out-of-bounds write in the wrong circumstances. The other involved slice::join(), where repeated calls to .borrow() could behave differently under a pathological but valid Borrow implementation, opening the door to heap corruption.

These are not beginner mistakes. They are not sloppy "forgot to free memory" bugs. They live in the uncomfortable territory where assumptions, invariants, edge cases, and rare execution paths meet.

That is exactly why I find this story so interesting.

For years, many of us have treated AI coding tools as productivity tools. They help write boilerplate. They suggest tests. They speed up documentation. Sometimes they generate code that is surprisingly decent. Sometimes they generate code that is confidently wrong. Most of the public discussion stays trapped there.

But this feels different.

This is not about AI helping somebody scaffold a CRUD app faster.

This is about AI being pointed at foundational code and apparently finding issues subtle enough that they survived in one of the most carefully designed programming ecosystems we have.

That should get our attention.

What I like about Rust culture is that, at its best, it has never really depended on fantasy. Rust people talk about invariants. Contracts. Unsafe blocks. Edge cases. Failure modes. The language is ambitious, yes, but the engineering mindset around it is usually pretty grounded. Rust does not work because programmers became smarter or more virtuous. It works because the language and tooling make dangerous things more visible and make certain mistakes harder to express.

So to me, AI-assisted security review feels less like a disruption of the Rust philosophy and more like an extension of it.

It is another tool for pressure-testing assumptions.

And assumptions are where a lot of real bugs hide.

That is probably the part of software engineering I have come to respect more over time. Not cleverness. Not syntax mastery. Not even speed. Just the ability to ask: what am I assuming here without realizing it?

Am I assuming this value cannot change between calls?

Am I assuming allocation failure does not matter in practice?

Am I assuming a safe trait will behave in the "reasonable" way rather than the technically permitted way?

Am I assuming some invariant holds because it usually holds?

A lot of nasty bugs are waiting behind those questions.

The older I get, the less impressed I am by code that looks elegant on the surface, and the more impressed I am by code that survives hostile reality. Weird inputs. Strange trait impls. Rare panic paths. Bad timing. Low-memory conditions. All the ugly stuff that almost nobody wants to think about while writing code.

That is why these Rust standard library issues matter, even if the publicly disclosed ones are described as minor.

They are a reminder that "safe language" does not mean "finished security story."

It means better defaults.

It means a smaller blast radius.

It means you have already removed a shocking amount of risk before the program even runs.

But it does not mean the work is over.

And maybe that is the most useful way to read this whole story.

Not as "look, Rust has bugs too."

That take is lazy.

Of course Rust has bugs too. Every meaningful software system has bugs. The real question is what kind of bugs are left, how hard they are to introduce, how hard they are to exploit, and how quickly they can be found and fixed.

What feels new here is the "how they can be found" part.

I think we are entering a period where security review will become much more asymmetrical.

A determined human reviewer gets tired. They miss things. They follow instinct. They skip paths that feel too unlikely. They focus on what looks suspicious.

A powerful model does not have human intuition in the same way, but it also does not get bored in the same way. It can poke at edge cases all day. It can follow odd assumptions longer than most people would. It can ask annoying questions at scale.

That does not make it magical. It does make it useful.

And if that capability is already finding subtle issues in something as scrutinized as Rust's standard library, it is hard not to wonder what it will mean for the rest of the software world, where review is often rushed, understaffed, and nowhere near this rigorous.

Personally, I do not read this story as a warning against Rust.

I read it as a warning against complacency.

Rust is still one of the most important advances in systems programming in a very long time. I believe that. But language design alone will never be enough. The real world always pushes back. The weird cases always show up eventually. The contract you thought was obvious turns out not to be guaranteed. The invariant you trusted turns out to be more fragile than it looked.

And now we have machines that are getting better at finding those fractures.

That should make maintainers uncomfortable, yes.

But I also think it should make them optimistic.

Because the same shift that makes vulnerability discovery more powerful can also make defense better. It can make audits deeper. It can make reviews broader. It can force libraries to tighten assumptions that used to go unquestioned. It can help teams find the weird stuff before attackers do.

That, to me, is the real story here.

Claude Mythos finding bugs in Rust's standard library is not a symbol of failure.

It is a glimpse of what modern software assurance might start to look like.

Less mythology. More scrutiny.

Less confidence theater. More adversarial review.

Less "this language is safe, so we're done here." More "this language helps a lot, now let's keep digging."

And honestly, that is the kind of future I trust more.

AI Assisted Rust Security : https://tobiweissmann.gumroad.com/l/rhsdn