AMD processors - frequency scaling / power management: A remote or local attacker times operations and infers secret

Impact

A remote or local attacker times operations and infers secret data from how DVFS frequency scaling responds to the data being processed - turning a power side channel into a timing side channel that works over the network. On a GPU host node the exposure is the CPU-side crypto: TLS termination for your API, key material in the control plane, tenant secrets handled by the host. It does not read GPU memory.

Who can reach it

An authenticated attacker able to time operations on the target, including remotely for network-facing crypto. Co-tenancy is not required, which is what made Hertzbleed notable.

What to do

AMD's guidance is not a microcode patch: the fix is constant-time or blinded implementations in the affected cryptographic software, and optionally disabling frequency boost - which costs you real performance on every workload on the node. Practically: update OpenSSL/libcrypto and any SIKE-like primitives, and treat disabling boost as a last resort. Effectively UNPATCHABLE at the silicon level.

References