Definition
Meltdown is a hardware vulnerability that allows unauthorized processes to read memory from privileged locations, such as the kernel or other applications. It exploits a performance optimization technique called speculative execution, where the processor guesses future instructions and executes them before they are confirmed. This allows an attacker to trick the CPU into revealing sensitive data that it should not have access to. For example, a malicious website could potentially read passwords or credit card numbers stored in your browser's memory. Unlike Spectre, which targets the same speculative execution mechanism but in a different way, Meltdown specifically targets the bounds checking of memory access. This critical vulnerability is often covered in cybersecurity certifications like CompTIA Security+ and CISSP.