Recent discoveries have unveiled two significant attacks targeting AMD SEV-SNP-protected virtual machines (VMs), potentially allowing malicious hosts to access sensitive data. These findings raise critical concerns about cloud security, especially for those relying on AMD’s EPYC server processors designed to keep host operators at bay.
Mior and Skyfall: Detailed Vulnerabilities
The two attacks, named Mior and Skyfall, were demonstrated in controlled environments on AMD EPYC processors. Mior, notably, can alter VM memory and falsify attestation reports, requiring control over the server’s hypervisor and BIOS. Conversely, Skyfall leverages transient scheduler attacks to expose VM data via instruction timing, leaving VM state data accessible post-failure.
In experiments, the ETH Zurich team exploited SEV-SNP’s start-up phase, manipulating the Platform Security Processor (PSP) to redirect memory writes. This oversight allowed unauthorized RMP modifications, enabling memory access and debugging within a confidential VM. The effectiveness of these methods was consistently proven across numerous trials.
Implications for AMD’s Confidential Computing
AMD’s SEV-SNP technology aims to safeguard VMs through hardware-enforced encryption and access controls. However, the demonstrated vulnerabilities compromise this security promise by allowing hypervisor-level attacks. The research indicates that while Mior requires BIOS tampering, Skyfall can operate without physical hardware interference, broadening its potential threat scope.
These vulnerabilities, tracked as CVE-2026-0462 for Mior and CVE-2026-40671 for Skyfall, affect several AMD EPYC server lines. The upcoming firmware and microcode updates from AMD, scheduled for late 2023 and early 2024, are anticipated to mitigate these risks.
Future Outlook and Mitigation Efforts
AMD advises customers to seek BIOS updates from their server manufacturers to address these flaws. The company has started rolling out patches, with additional updates expected shortly. However, the effectiveness of these patches, whether standalone or in conjunction with BIOS updates, remains to be clarified.
As cloud providers implement these updates, users of confidential VMs must rely on their service providers for timely installations. The ongoing collaboration between AMD and cybersecurity researchers underscores the importance of proactive security measures in addressing emerging threats.
While there have been no reports of these vulnerabilities being exploited in the wild, the availability of proof-of-concept code highlights the urgency for affected parties to implement the recommended security patches promptly.
