Meltdown

Meltdown is a security vulnerability that affects processors that use speculative execution, which is a technique used to improve performance by predicting the outcome of instructions before they are executed. The vulnerability was first discovered in 2018, and it affects processors from multiple vendors, including Intel, AMD, and ARM...

In the case of iOS specifically, it affects all iOS devices that are powered by an affected processor, which includes iPhones and iPads. The vulnerability allows an attacker to access sensitive information from the kernel memory, which is the part of the memory that is used by the operating system to manage the system's resources. This can include sensitive information such as login credentials, cryptographic keys, and other sensitive data.

Apple released an update to iOS 11.2 to fix the vulnerability. However, it's important to note that the vulnerability cannot be completely eliminated by a software update, as the vulnerability is caused by a design flaw in the affected processors.

As a result, Apple has also implemented additional mitigations in iOS to help protect against this vulnerability. These include a technique called kernel page table isolation (KPTI), which separates the kernel memory from the user memory, making it more difficult for an attacker to access the kernel memory.

It's worth noting that Meltdown is not the only vulnerability that affects speculative execution, there are other speculative execution vulnerabilities such as Spectre, and ZombieLoad that were discovered in 2018 and 2019, which also have the same kind of impact and solution.