Recent security research has unveiled critical vulnerabilities within the Trusted Execution Environments (TEEs) of AMD and Intel processors, exposing significant risks to the integrity of cloud-based virtual machines. The studies, conducted by teams from Graz University of Technology, the Fraunhofer Institute for Secure Information Technology, and other institutions, introduced new attack vectors named CounterSEVeillance and TDXDown. These vulnerabilities primarily target AMD’s Secure Encrypted Virtualization (SEV) technology and Intel’s Trust Domain Extensions (TDX), which are designed to isolate sensitive applications and protect data from unauthorized access.
The CounterSEVeillance attack exploits AMD’s SEV-Secure Nested Paging (SEV-SNP) feature, which is intended to safeguard confidential virtual machines running in shared environments. By leveraging performance counters—metrics that monitor hardware events such as executed instructions and cache misses—attackers can conduct side-channel attacks. Researchers demonstrated that by employing a technique called single-stepping, they could analyze the execution of instructions within a TEE, allowing them to recover sensitive information, including cryptographic keys, from confidential virtual machines. For instance, they successfully extracted a full RSA-4096 key and recovered time-based one-time passwords (TOTPs) using this method.
Intel is not exempt from scrutiny, as the TDXDown attack highlights vulnerabilities in its TDX technology, which also aims to protect sensitive workloads from unauthorized access. Researchers have shown how flaws in TDX’s mitigation mechanisms could be exploited to conduct single-stepping attacks, similar to those observed in AMD’s SEV technology. This dual vulnerability landscape poses serious concerns for organizations utilizing these processors in cloud environments, where privileged access could allow a malicious actor, such as a compromised cloud service provider, to exploit these weaknesses.
In response to these findings, both AMD and Intel have acknowledged the vulnerabilities and have issued advisories for developers. AMD clarified that performance counters are not protected under SEV and advised implementing best practices to minimize risks. Intel, while having updated TDX to address the TDXDown vulnerability, classified it as a low-severity issue, asserting minimal real-world risk. Nevertheless, these developments underscore the need for continuous scrutiny and enhancement of security measures surrounding TEEs, particularly as sophisticated attacks evolve in the landscape of cloud computing.
