[tptacek]

I'm not asking why they'd need to go threat-hunting if there was an ICMP kernel RCE in Linux. CopyFail requires someone untrusted running shell commands somewhere. Where is that exposure in their architecture?

I'm asking because I don't think they have such an exposure.

[Yoric]

At the very least, Cloudflare hosts web workers, which let a customer execute more-or-less arbitrary wasm code on their servers. If there's an exploit that lets you escape the wasm sandbox, copy.fail can be chained into (afaiu) an exploit against the Linux host. That's a pretty big risk.

Also, Cloudflare hosts some AI services, so it's possible that some consumers are running Python code in their containers, without the wasm sandbox.

[tptacek]

If there's a direct link from Cloudflare workers / WASM to uid=nobody execve or arbitrary syscalls on their hosts, they're already fucked, so I don't think that's true.

[HDBaseT]

I don't understand your point.

You seem so pressed on the fact "why would they even patch this!!!", maybe because its best practice to patch things? You never known what things could be chained together, so you might as well patch this, given its so obviously bad.

[js2]

That's a straw man and not what he asked. Literally, he asked: "why they would have been vulnerable to CopyFail?"

I've been a sysadmin/programmer since the mid-90s. Local root exploits are a dime a dozen. If your infrastructure relies upon the tenuous difference between root and non-root accounts, you've already lost. Cloudflare isn't an ISP handing out shell accounts on Unix machines.

So again, yes, of course you should patch your Linux machines. Defense in depth and all that. But the question remains: "why Cloudflare would have been vulnerable to CopyFail?" (in anything but an academic sense). Because I do not believe that they can possibly be relying on the difference between root and non-root account.

[HDBaseT]

I don't care about your credentials. It doesn't take a genius to realize that having known major security holes is not ideal.

It is pretty clear they aren't too concerned about this being a issue for this business, after the first paragraph in bold on the blog:

"There was no impact to the Cloudflare environment, no customer data was at risk, and no services were disrupted at any point. Read on to learn how our preparedness paid off."

As mentioned, you never want to give options to a potential attacker/exploit by keeping known vulnerabilities present in your system. You cannot always predict every single avenue an attack could leverage.

Imagine having a data center with barbed wire fences, guard posts, security and cameras covering every square meter of the facility. You wouldn't just leave a door right open because in theory, people shouldn't be able to walk right in. But why would you willingly leave a door open? Even if the possibility is 0.000001%?

People like you would be the first to turn and say "Cloudflare are morons for not patching this!!! Me and my 1 billion years experience and goat status would of prevented this' when some major Cloudflare hack occurs and it was found that phishing 30 different people and using 9 different exploits (including Copyfail) allowed the attacker to bring down Cloudfare

[saurik]

I mean, in some sense, Cloudflare simply accepts the security posture of "already lost", right? They run workloads for multiple users within the same process separated by nothing more than V8 boundaries, which even Chrome (which always claimed to run tabs in separate processes but actually didn't due to various edge cases) finally stopped doing (now afaik they do fence origins within processes) as it was so risky... Cloudflare's best lines of defense past "we patch often" are merely that they sort of KYC at least most of their users so they can log everything they run with their identity and that they take users of similar trust levels (age of account, level of KYC, amount of usage, etc.) and group those into processes... but, at the end of the day, they rely on something that I would certainly never consider reasonable to ship in production.

[js2]

> They run workloads for multiple users within the same process

Ah, then the root/non-root distinction means even less. They don't even distinguish between non-root accounts! Again, I'm not arguing against them defensively patching their systems against known exploits—they'd be crazy not to; just agreeing with Thomas that they can't be relying upon protecting root from non-root accounts as part a normal operational security boundary.

To wit: if an attacker escapes V8, it's unclear that leveraging "Copy Fail" to escape from non-root to root buys the attacker a whole lot more.