Toward Verifiable Microcode: Reverse Engineering AMD Zen5 Update

No ratings

Presented at Area41 Conference 2026 by

Kaya Ercihan

Antonio Blanco

Microcode updates provide processor vendors with a mechanism to change internal control behavior after manufacturing, for example to mitigate faulty or vulnerable execution paths without redesigning silicon. As a result, microcode forms a security-critical but largely opaque layer of modern CPUs. This work presents a structured reverse-engineering study of AMD Zen 5 microcode updates with the goal of moving toward verifiable microcode. We reconstruct the patch format from public kernel sources and corpus-level validation, identify the major structural regions of AMD microcode patches, and separate metadata, cryptographic material, redirection state, and executable payload. To support systematic analysis, we build a workflow for collecting, parsing, extracting, and normalizing AMD microcode patches, and implement the resulting format knowledge in a Binary Ninja plug-in that exposes patch structure as well as revision and loader identifiers directly in the analysis environment. We further analyze encrypted and non-encrypted payloads and apply statistical profiling to obtain initial opcode tags and heuristic control-flow candidates. The resulting methodology and tooling establish a reproducible basis for future work on decryption, instruction classification, and differential analysis of security-relevant microcode revisions.