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Encryption-breaking, password-leaking bug in many AMD CPUs could take months to fix

https://arstechnica.com/information-technology/2023/07/encryption-breaking-password-leaking-bug-in-many-amd-cpus-could-take-months-to-fix/

"Zenbleed" bug affects all Zen 2-based Ryzen, Threadripper, and EPYC CPUs.

The bug allows attackers to swipe data from a CPU’s registers. […] the exploit doesn’t require physical hardware access and can be triggered by loading JavaScript on a malicious website.

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TheFloydist

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I suppose that is a good point. look for repeating chunks of data to get hardware encryption keys. However, the main point I want to stress remains that a javascript version is yet to be proven. Cloudflare edited their original statement yesterday from "The attack can even be carried out remotely through JavaScript on a website, meaning that the attacker need not have physical access to the computer or server." to today "While there might be a possibility to execute this attack via the browser on the remote machine it hasn’t been yet demonstrated." https://blog.cloudflare.com/zenbleed-vulnerability/

This was the main piece of misinformation I wanted to dispel. It is still up in the air whether regular people with home computers need to be panicking. Thank you for also pointing out that this isn't primarily targeting passwords "typed by users."

jarfil

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The JavaScript vector is a reasonable extrapolation based on how similar attacks like Meltdown, Spectre, or Heartbleed, eventually got their JavaScript exploits. There may not be one yet, but there's likely to be one at some point.

It is still up in the air whether regular people with home computers need to be panicking.

That one's easy: no, they don't.

Even if an attacker were to get the disk encryption key from a regular user through some malicious JavaScript, the chances of them being able to actually exploit it, are slim to none. They'd still need some extra way to use that key, which would require a separate exploit, or physical access.

If it were a company computer, or the user got personally targeted (espionage, trade secrets, law enforcement, etc.)... then maybe worry a bit.

Hosting providers with shared servers, need to panic a lot. Anyone running a public server, be it at a provider or at home, should also panic a bit.

cwagner

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jarfil

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Tailscale... accessible from where? It would likely require an attacker to jump from the endpoint to a vulnerable application (or SSH) which, while possible, seems improbable. Maybe over time as the exploit gets packaged in more suites, or if targeted personally.

On the VPS, check cpuinfo to see if it's one of the vulnerable ones. If it is, then I'd either ask them directly, avoid that kind of VPS for a while, or use it for non-sensitive stuff until it gets a fix.

ARM... will have its day. Speculative branching is too tempting to ignore, and too difficult to implement flawlessly. Just give them time 😉

cwagner

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