AmdPspP2CmboxV2 - SMM input validation (AMD-SB-7027): MULTI-TENANT ISOLATION: Insufficient input validation

Impact

MULTI-TENANT ISOLATION: Insufficient input validation in the AmdPspP2CmboxV2 SMM driver - the PSP mailbox interface - lets ring-0 code overwrite SMRAM and execute at SMM. This one is notable for sitting on the PSP communication path, so a single bug hands the attacker both the SMM context and a channel to the secure processor.

Who can reach it

Local, ring-0 on the host.

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.

References