AMD SEV firmware - improper initialization corrupting RMP-covered memory: MULTI-TENANT ISOLATION: An initialization

Impact

MULTI-TENANT ISOLATION: An initialization defect in SEV firmware lets an admin-privileged attacker corrupt memory covered by the RMP, costing confidential guest integrity. Same family as the other RMP issues in this batch and shipped in the same AMD advisory wave - the recurring theme is that SNP's protections are only as good as the firmware that sets them up.

Who can reach it

Local, admin-privileged.

What to do

Fixed in AMD reference firmware (AGESA / PSP / SEV firmware) and delivered only as an OEM SBIOS/BIOS package - Dell, HPE, Supermicro, Lenovo and the ODMs each rebuild and requalify AMD's AGESA drop before shipping. **Expect one to six months of OEM lag**, and on end-of-support platforms expect nothing. Applying it is a drain plus full power cycle, not a driver reload. Verify by reading back the PSP/SMU firmware version afterwards rather than trusting the BIOS version string. This sits inside the SEV-SNP trust boundary, so the update moves the platform's reported TCB version: refresh VCEK certificates from AMD's KDS and update any attestation policy your tenants pin, or confidential guest launches will start failing right after the BIOS lands.

References