A memory model is the set of rules that defines how software expects memory to behave: how values are stored, read, updated, and seen by different parts of a program. It is an abstraction, not the physical machine itself. Different languages, compilers, and CPUs can follow different rules about ordering, visibility, and consistency.
This matters in cybersecurity because many bugs start when code relies on assumptions the memory model does not guarantee. Race conditions, stale reads, and incorrect synchronization can make programs behave unpredictably, especially in multithreaded or low-level code. Attackers can sometimes exploit these weaknesses to cause crashes, bypass checks, or influence program logic. Defenders use a clear understanding of the memory model to write safe concurrent code, choose correct locking or atomic operations, and avoid dangerous assumptions about when data changes become visible.