Colin Percival

This affects recent Intel CPUs. It might affect non-Intel CPUs but I have no evidence of that. It is an information leak caused by speculative execution, affecting operating systems which use "lazy FPU context switching".

The impact of this bug is disclosure of the contents of FPU/MMX/SSE/AVX registers. This is very bad because AES encryption keys almost always end up in SSE registers.

You need to be able to execute code on the same CPU as the target process in order to steal cryptographic keys this way. You also need to perform a specific sequence of operations before the CPU pipeline completes, so there's a narrow window for execution.

I'm not going to say that it's *impossible* that this could be executed via a web browser or a similarly "quasi-remote" attack, but it's much harder than Meltdown was.

I was not part of the coordinated disclosure process for this vulnerability. I became aware of this issue after attending a session organized by Theo de Raadt at @BSDCan. It took me about 5 hours to write a working exploit based on the details he announced.

Theo says that he was not under NDA and was not part of the coordinated disclosure process. I believe him. However, there were details which he knew and attributed to "rumours" which very clearly came from someone who was part of the embargo.

My understanding is that the original disclosure date for this was some time in late July or early August. After I wrote an exploit for this, I contacted the embargoed people to say "look, if I can do this in five hours, other people can too; you can't wait that long".

While I have exploit code and it is being circulated among some of the relevant security teams, I'm not going to publish it yet; the purpose was to convince the relevant people that they couldn't afford to wait, and that purpose has been achieved.

I know from the years that I spent as FreeBSD security officer that it takes some time to get patches out, and my goal is to make the world more secure, not less. But after everybody has had time to push their patches out I'll release the exploit code to help future researchers.

I think that's everything I need to say about this vulnerability right now. Happy to answer questions, but I'm not part of the FreeBSD security team and don't have any inside knowledge here -- FreeBSD takes embargoes seriously and they didn't share anything with me. </thread>