AMD Issues Updates for Silicon-Level 'SinkClose' Processor Flaw

AMD processors (EPYC datacenter and Ryzen PC/embedded lines) contain a long-standing silicon-level flaw called "SinkClose" that allows modification of System Management Mode (SMM) protections via improper MSR validation, enabling potential persistent, hard-to-detect bootkits. IOActive researchers demonstrated the SMM bypass leveraging legacy compatibility features (TClose), affecting hundreds of millions of devices; AMD has published mitigations and product security guidance, but exploitation requires kernel-level access and advanced knowledge of AMD chip architecture.