Originally published on April 26, 2024.

Preface: (Level 3 cache) A memory bank built onto the motherboard or within the CPU module. The L3 cache feeds the L2 cache, and its memory is typically slower than the L2 memory, but faster than main memory.

Background: The last-level cache (LLC) is the last chance for memory accesses from the processor to avoid the costly latency of going to main memory. Level 3 (L3) represents the Last Level Cache (LLC) in the example above, and is the last (and slowest) stop within the cache hierarchy before the system must endure the long trek out to Main Memory.

The last-level cache (LLC) is one of the most dangerous shared resources since it is shared by all of the cores in a processor package, yet it allows fine-grained, high-bandwidth, low-noise cross-core attacks.

The cache memory divides into three levels:

L1 cache – fastest, but smallest, data and instructions

L2 cache – slower, but bigger, data-only

L3 cache – slowest, but biggest, data-only

Vulnerability detail: Cache side channel attacks work by monitoring security-critical operations such as AES T table entries or modular exponentiation or multiplication or memory accesses. The attacker is then able to derive the encryption key by recovering the key based on the accesses made (or not made) by the victim.

Official announcement: Please refer to the link for details –

https://www.amd.com/en/resources/product-security/bulletin/amd-sb-7019.html