Intel SGX and AMD SEV-SNP / DRAM interposer (memory aliasing): MULTI-TENANT ISOLATION: Battering RAM: a cheap DRAM

Impact

MULTI-TENANT ISOLATION: Battering RAM: a cheap DRAM interposer that aliases physical addresses so the same ciphertext is served for two different locations, defeating the memory-encryption protections of both Intel SGX and AMD SEV-SNP and giving the attacker plaintext access to enclave and confidential-VM memory. Same operator conclusion as WireTap and it generalises across both vendors' confidential-compute stacks, so it is not a reason to switch silicon.

Who can reach it

Physical access to install an interposer on the DIMM path. Applies to any deployment where hardware is not continuously in your physical custody.

What to do

No firmware or microcode fix on affected parts - the attack targets a design property of deterministic memory encryption. Treat confidential compute as protecting against a remote or software-privileged adversary, not a physical one, and write that into what you tell customers. Physical security, tamper-evident hardware and custody controls are the actual mitigation.

References