Privasys Fixes Critical TLS Relay Flaw in Enclave OS Mini SGX Runtime

Privasys has released a security update for Enclave OS Mini that resolves a critical vulnerability allowing attackers to impersonate attested Intel SGX enclaves through relay attacks. The flaw, tracked as CVE-2026-108265, affected versions of the Rust-based runtime prior to wasm-v0.40.0.

The vulnerability stems from a design flaw in the Remote Attestation (RA) process for TLS connections. According to the National Vulnerability Database, the RA-TLS challenge certificate path placed the certificate public-key hash and client nonce into the quote ReportData. However, this data structure omitted a value bound to the active TLS session.

This missing binding created a window for exploitation where an attacker who had obtained an enclave’s TLS private key could relay a genuine quote onto a different connection. Consequently, a relying party would accept the attacker-terminated connection as the legitimate, attested enclave, bypassing the intended security guarantees of the confidential computing environment.

Technical Context and Severity

The National Vulnerability Database assigns CVE-2026-108265 a CVSS score of 9.1, classifying it as Critical. The weakness is categorized under CWE-346, which relates to comparison of incorrect value. In the context of Intel SGX, remote attestation is a critical mechanism that allows a remote party to verify that code is running inside a genuine, unmodified enclave. By failing to bind the attestation quote to the specific TLS session, the runtime allowed the cryptographic proof of identity to be decoupled from the communication channel. This decoupling enables a man-in-the-middle style relay attack, where the authenticity of the enclave is proven, but the connection is not.

Privasys Enclave OS Mini is designed as a runtime for confidential applications inside Intel SGX enclaves. The integrity of these enclaves relies heavily on the correctness of the attestation flow. The omission of the session-bound value meant that the attestation evidence could be replayed or redirected, undermining the trust model that relies on the one-to-one mapping between the attested enclave and the client connection.

Affected Systems

The vulnerability affects Privasys Enclave OS Mini versions prior to wasm-v0.40.0. Organizations and developers utilizing this specific Rust-based runtime for building confidential applications on Intel SGX hardware are at risk if they are running older versions. The impact is most severe in deployments where remote attestation is used to establish trust with relying parties, as the flaw allows an adversary with access to the enclave’s TLS private key to successfully impersonate the enclave to external systems.

What should you do?

Privasys has addressed this issue in version wasm-v0.40.0. Users of Enclave OS Mini should verify their current version and upgrade to wasm-v0.40.0 or later to mitigate the risk of relay attacks. Until an update is applied, the risk remains that an attacker with possession of the TLS private key can compromise the integrity of the attestation process.