Advanced Micro Devices (AMD) has disclosed a high-severity vulnerability (CVE-2024-56161) in its Secure Encrypted Virtualization (SEV) technology, specifically impacting SEV-SNP-powered confidential computing systems.
If successfully exploited, this flaw could compromise the confidentiality and integrity of virtual machine guests, leaving sensitive workloads exposed.
The vulnerability arises from improper signature verification in the microcode patch loader of AMD CPUs, enabling attackers with local administrator privileges to inject malicious microcode.
Vulnerability Details
The vulnerability, reported by researchers from Google, poses a significant risk for AMD EPYC processors across several generations, including Naples (EPYC 7001), Rome (EPYC 7002), Milan (EPYC 7003), Milan-X, Genoa (EPYC 9004), and Bergamo/Siena.
AMD has rated the flaw with a CVSS score of 7.2, indicating its high potential impact.
CVE-2024-56161 allows attackers with privileged access to bypass SEV-SNP’s signature verification process, enabling unauthorized microcode to compromise the security of confidential guests in virtualized environments.
Firmware Updates
AMD has provided mitigations through updated microcode and SEV firmware releases.
System administrators are advised to apply the latest Platform Initialization (PI) updates and ensure their BIOS firmware contains the necessary fixes.
Microcode updates specific to each affected EPYC processor have been delivered, with AMD providing details on minimum firmware requirements.
For example, Milan processors require MilanPI 1.0.0.F2 with uCode version 0x0A0011DB and SEV firmware 1.55.40 to mitigate the vulnerability.
Similarly, Genoa processors require GenoaPI 1.0.0.E3 or newer.
The updates introduce additional safeguards to prevent hot-loading of older, vulnerable microcode, which could otherwise open the door to potential attacks.
After applying the patches, administrators should reboot systems to activate the updated microcode.
Confidential guests can verify that mitigations are in place on host platforms through SEV-SNP attestation reports.
This vulnerability was responsibly disclosed to AMD by a team of researchers from Google, including Josh Eads, Kristoffer Janke, Eduardo Vela Nava, Tavis Ormandy, and Matteo Rizzo.
AMD acknowledged their efforts in coordinated vulnerability disclosure and acted swiftly to deliver mitigations.
Organizations utilizing AMD EPYC processors with SEV, SEV-ES, or SEV-SNP-enabled workloads should immediately contact their Original Equipment Manufacturer (OEM) to obtain the latest BIOS updates.
Failure to deploy the updates could leave systems vulnerable to local privilege escalation attacks, potentially resulting in the exposure of sensitive data hosted in virtualized environments.
AMD warns that this vulnerability underscores the importance of maintaining up-to-date microcode and BIOS configurations to safeguard against emerging threats in secure computing.
This disclosure serves as a reminder that, while technologies like SEV-SNP enhance workload security, they require continual updates to address evolving attack vectors.
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