AMD SEV firmware - use-after-free allowing a SINGLE_SOCKET guest to activate on the wrong socket (AMD-SB-3023)

Impact

MULTI-TENANT ISOLATION: A use-after-free in SEV firmware lets a migrated guest whose policy specifies SINGLE_SOCKET be activated on a different socket than its migration agent. The guest chose that policy to constrain where its keys and memory live; violating it silently means a tenant's stated confidential-computing constraint is not being enforced, and they have no way to tell.

Who can reach it

Malicious hypervisor driving guest migration.

What to do

Fixed in AMD PI/AGESA firmware and delivered only as an OEM SBIOS package - AMD ships the PI drop to Dell, HPE, Supermicro, Lenovo and the ODMs, who each requalify before releasing BIOS. **Budget one to six months of OEM lag**, and note that several CVEs in this batch are marked 'no fix planned' on Naples (EPYC 7001) - for those the only remediation is retiring the hardware. Applying it means cordon, drain and a full power cycle per node; there is no driver reload, no live patch and no VBIOS step. Because this touches the SEV-SNP trust boundary, the update moves the platform TCB version: refresh VCEK certificates from AMD's KDS and update tenant attestation policy, or confidential guest launches will fail immediately after the BIOS lands. Worth flagging to any tenant who sets socket-scoped SNP guest policies - if you sell policy enforcement as a feature, this is a period during which it was not enforced.

References