I don't know, to me, this sounds like one of the more subtle examples of the kinds of mistakes that lead to security failures. Like, it might be an almost archetypical example of the "all bugs are security vulnerabilities" hypothesis. They got code execution from expm1!

But if you believe that this is an example of wanton abuse at Google, you can trade on that belief, and in a sense put your money where your mouth is, because this is a whole class of potential bugs, not just one bug; the same pattern will recur for other places where the v8 typer is wrong about the possible results of functions. Go do a sweep! If you find one, the value of the resulting bug might be pretty decent.

> it might be an almost archetypical example of the "all bugs are security vulnerabilities" hypothesis

This article will be my new go-to example when someone handwaves a bug away with a complacent “it’ll never happen” and “it’s not that big of a deal”. Yes it will, and yes it is.

Right, and it is right up there with https://www.blackhat.com/us-18/briefings/schedule/index.html, whose security value was unappreciated by some very smart folks.

Were you trying to link to a specific briefing? Your link just goes to the full schedule for me.

Yes, sorry about that

https://www.blackhat.com/us-18/briefings/schedule/index.html...

If they just didnt discard the OutOfBounds check, the V8 JS engine would be a lot safer...

...and probably a lot slower. Google loves to make claims about V8's performance, but not so much about security.

certainly V8 tries to be correct and this bug will be fixed. Chromium's position is "security in depth". They know it's impossible to have zero bugs therefore the entire architure assumes there will be bugs and tries to prevent them from causing any harm. This is also why there are roughly 10x less code execution bugs in chrome vs other browsers. same number of bugs overall but most lead nowhere

> Chromium's position is "security in depth".

Yet the exploit in WebSQL a few weeks ago gave RCE from a component directly reachable by page scripts.

Technically that was an SQL injection attack. :)

That must have been one of the bugs that lead somewhere.

I wouldn't be surprised if NegativeZero got introduced to fix some other bug along the same lines involving a different function, and when fixing that bug they neglected to notice that it applies to expm1 as well. Math.expm1 is... a bit obscure. I could certainly see myself making the same mistake.

> how is there not an automated set of tests that use one out of every other IEEE754-associated type as input to then check whether it generates output which falls outside the assumed set of types?

It's slightly worse than that. Math.expm1(-0) = -0 is explicitly called out as part of the standard[1]. You don't need to throw every IEEE754 at your functions to make sure they're all correct, but validating the explicitly defined corner cases is table stakes.

1. https://www.ecma-international.org/ecma-262/6.0/#sec-math.ex...

serious question - does the V8 team do property checking?