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Processor vulnerability

CVE-2020-12966

A malicious hypervisor can infer an SEV-ES or SEV-SNP guest's register values from the ciphertext of its saved state, which defeats constant-time cryptography.

Name
Ciphertext side channel on SEV-ES register state
Also known as
CIPHERLEAKS
Vulnerability
AMD SEV, SEV-ES and SEV-SNP
Kind
Other
CVE published
2022-02-04 CVE record
Advisories
AMD-SB-1013
When an SEV-ES guest exits, its registers are saved in memory, encrypted. A malicious hypervisor that watches that ciphertext over time can infer the register values and from them secrets; the paper AMD names (CIPHERLEAKS, USENIX Security 2021) did this to constant- time cryptography. AMD’s fix is VMSA register protection, part of SEV-SNP, delivered in MilanPI-SP3 1.0.0.5.

Affected processors

3 of the 3 microarchitectures listed are affected in all or some of their models.

What the sources say of each microarchitecture.
MicroarchitectureStatusDetailSource
ZenAffectedFirst generation EPYC: no SEV-SNP, no fixamd.com
Zen 2AffectedSecond generation EPYC: no SEV-SNP, no fixamd.com
Zen 3AffectedThird generation EPYC: VMSA register protection, MilanPI-SP3 1.0.0.5amd.com

Mitigations

  • Firmware: VMSA register protection, which needs SEV-SNP, in MilanPI-SP3 1.0.0.5 for the third generation of EPYC. Source.

Sources

  1. AMD-SB-1013: AMD Secure Encryption Virtualization (SEV) Information Disclosure