What is the Meltdown vulnerability?


The Meltdown vulnerability is a serious security flaw found in certain microprocessors. It primarily involves the improper enforcement of permission checks during memory access operations. In a Meltdown attack, the processor speeds up these operations by performing permission checks in parallel with memory access. This leads to the potential for sensitive data breaches as malicious processes could exploit this parallelization to access privileged data without proper authorization.

Jon Masters, a notable figure in computer architecture, explains how Meltdown happens when a processor, trying to optimize performance, checks permissions while also accessing memory, assuming most programs have benign intentions. However, if this assumption fails, it allows programs to bypass security checks and potentially access data they shouldn't be able to access 1 .

Cache Behavior Exploitation

Jon explains how caches can be exploited to infer information about other execution happening on the processor. He also discusses the egregious mistake of Meltdown, where permission checking is not properly enforced in vulnerable processors.

On The Metal

Jon Masters