The TEE.fail attack

Notes and a critical review of TEE.fail: Breaking Trusted Execution Environments via DDR5 Memory Bus Interposition, written as coursework at Hochschule Flensburg. The attack and its findings are the work of the TEE.fail authors.

Abstract

Trusted Execution Environments (TEEs) are a commonly used technology to provide strong security guarantees for sensitive data, running on an untrusted environment, which could be a compromised operating system or hypervisor. This security property is especially attractive for cloud environments, as it prevents cloud providers from also accessing sensitive information. Utilizing this advantage for cloud-scale, TEEs have evolved from protecting only small parts of a system to safeguarding whole virtual machines. This required significant architectural changes favoring scalability and performance over strong security guarantees. This paper summarizes the findings of TEE.fail, a study that demonstrates a ciphertext-based side-channel attack on TEEs that, assuming the environment's security guarantees were true, would be impossible. Exploiting deterministic memory encryption combined with weak integrity protection, enables the attacker to steal attestation keys and thereby break the entire trust foundation that TEE implementations rely on. The paper highlights the dangerous mismatch between the assumed threat models and the deployed system design, which violates the security that confidential computing attempts to offer and thus erodes trust in cloud environments.

Original paper

Jalen Chuang, Alex Seto, Nicolas Berrios, Stephan van Schaik, Christina Garman and Daniel Genkin. TEE.fail: Breaking Trusted Execution Environments via DDR5 Memory Bus Interposition. IEEE Symposium on Security and Privacy, 2026. Proceedings.