As reported yesterday the Linux and Windows kernels will receive a security update pretty soon to close vulnerabilities that concern 'kernel memory leaking'.
What exactly the design flaw is, that was probably identified at the end of 2017, is unknown to the general public. There is some speculation though.
Quote from the linked article:
Modern processors, like Intel's, perform speculative execution. In order to keep their internal pipelines primed with instructions to obey, the CPU cores try their best to guess what code is going to be run next, fetch it, and execute it.
It appears, from what AMD software engineer Tom Lendacky was suggesting above, that Intel's CPUs speculatively execute code potentially without performing security checks. It seems it may be possible to craft software in such a way that the processor starts executing an instruction that would normally be blocked – such as reading kernel memory from user mode – and completes that instruction before the privilege level check occurs.
That would allow ring-3-level user code to read ring-0-level kernel data. And that is not good.
The article also mentions a paper published in mid 2017, that describes a method to defeat KASLR.
I personally did not yet come across an attack that makes use of this method or any method that exploits the vulnerabilities that are now being fixed. Are there any?
As mentioned in the comments by Alexander these vulnerabilities have now been given the names Meltdown and Spectre.
Meltdown in short mean is a "novel softwarebased side-channel attack exploiting out-of-order execution on modern processors to read arbitrary kernel- and physical-memory locations from an unprivileged user space program". The linked paper as well as this post by Jann Horn of Google Project Zero are the go-to ressources regarding this vulnerability.
"Spectre attacks involve inducing a victim to speculatively perform operations that would not occur during correct program execution and which leak the victim’s confidential information via a side channel to the adversary." Again, the linked paper and the aforementioned GPZ post seem to be the go-to ressources.
Both papers present working attacks that exploit the vulnerabilities. My understanding so far is, that an attack against Spectre seems to be more impactful and more "portable" if you will, than an attack against Meltdown.open for discussion
This is why I want to shift this question towards Spectre and specify it in the following way:
Are there any known attacks - apart from the ones we saw in the Spectre paper or in other PoCs - that exploit the vulnerability known as Spectre?