![]() There are two good “kindergarten-class” analogies that may serve as useful introductions, which we have nicknamed the Helpful Grandson Analogy and the Book Voyeur Analogy. In order to understand how mitigations are being implemented, it’s important to grasp what the underlying issues are, which in turn requires an understanding of operating system and processor concepts. We have therefore provided the following risk grading: These issues affect practically every computer in server and end-user contexts, but due to the nature of the possible attack vectors, different use cases are exposed to different degrees. Other exploits that follow the patterns above almost certainly will emerge over time. ![]() Generally reading any kernel and user-space memory from userspace and VM-hosted applications, including memory belonging to other VMs and the hypervisor.Stealing hypervisor credentials, and reading secrets inside any hosted virtual machines from a malicious application running inside a virtualized guest, such as a public cloud instance.Reading passwords typed into web browsers, and reading images displayed on a web page from a separate, malicious application running on the same machine.Proof of concept code exploiting these vulnerabilities has been published that demonstrates: Once stolen, these can then be used to escalate privileges, which can then be used to modify the system or obtain sensitive information. ![]() Our Tech FAQ covers this and other aspects of the vulnerabilities in more detail.Īlthough an attacker can’t directly use Meltdown or Spectre to read disks or change anything on a system - for instance, to modify a password or write a file - the problem is that passwords, keys and other secrets are usually stored unencrypted in memory. Most end-users don’t associated running untrusted code with web browsing, so we must call out here that browser-hosted Javascript is an important attack vector, with advisories and updates being issued for both Mozilla/Firefox and Chrome browsers. Memory is not exposed at a very fast rate.The direct consequence of an attack is unrestricted, read-only access to all system memory.A CPU needs to be running untrusted code in order to be attackable.Second, due to the way the CPU is being tricked, the exposed memory can only be retrieved relatively slowly 2. This is not an arbitrary code execution issue, but rather that the CPU can be tricked by a malicious program to expose memory that it wouldn’t otherwise have access to. The essence of both vulnerabilities is that a program running on a computer can read memory it is not supposed to. In the spirit of Ubuntu, which is known for providing easily accessible technology - we are Linux for Human Beings, after all - this post attempts to provide an accessible description of the impact of these vulnerabilities and their mitigations. However, most of these statements focus on the mechanics of applying fixes and corresponding damage control, and not on explaining what the problems are, how the mitigations work, and how they may affect you.īecause the vulnerabilities and their fixes are CPU-dependent and involve a major performance-security tradeoff, understanding their general model is important to every system administrator and developer. As details of the Meltdown and Spectre vulnerabilities 1 have become clearer a number of statements have been published by the multiple vendors affected Canonical has issued advisories and updates on fixes and mitigations, the latest of which includes a first round of Spectre mitigations.
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