Dell PowerEdge Server BIOS (SMM communication buffer): The BIOS fails to properly validate the SMM communication

Impact

The BIOS fails to properly validate the SMM communication buffer, so a low-privilege local attacker can write into SMRAM. System Management Mode is the most privileged execution context on the machine - more privileged than the hypervisor, invisible to it, and reachable regardless of what OS is booted. An attacker who writes to SMRAM owns the node in a way that no reimage, no disk wipe and no hypervisor-level control removes. On a multi-tenant bare-metal GPU fleet this is the canonical persistent-implant primitive.

Who can reach it

A low-privilege local account on the host. Notably this does NOT need root or administrator - so a tenant workload running as an ordinary user is in scope, as is anything that gets modest code execution through an application bug.

What to do

System BIOS update. Stage it via iDRAC/Lifecycle Controller or OME, but it lands only on the next reboot, so it costs a job drain and a maintenance window per node. Per-platform version floors are in the advisory table. There is no config-only mitigation for an SMM handler bug - you cannot turn SMM off. Prioritise nodes that run untrusted or multi-tenant workloads over internal-only nodes when sequencing the rollout.

References