CVE-2026-108269 in RA-TLS Clients
Summary
by MITRE • 10/09/2026
Remote Attestation TLS Clients provides multi-language utilities for verifying attested TLS connections. Prior to 0.5.0, the Rust and Go RA-TLS challenge verifiers accepted quote ReportData that was bound to the certificate public key and client nonce but not to the active TLS session before permitting application traffic. An attacker who obtained an enclave TLS private key could relay a genuine quote onto another connection, causing the clients to accept an attacker-terminated connection as the attested enclave. This issue is fixed in 0.5.0.
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Analysis
by VulDB Data Team • 10/09/2026
The Remote Attestation Transport Layer Security (RA-TLS) protocol serves as a critical mechanism for establishing trust between remote enclaves and client applications by verifying that the connecting party possesses valid hardware-backed credentials. In versions of the RA-TLS utilities prior to 0.5.0, specifically within the Rust and Go implementations, a significant cryptographic binding flaw existed in the challenge verification process. The vulnerability stems from an incomplete scope of data inclusion during the generation and validation of attestation quotes. Specifically, while the quote ReportData was correctly bound to the certificate public key and the client nonce, it failed to incorporate any identifier or hash derived from the active TLS session itself. This omission created a gap in the cryptographic chain of trust that allowed for sophisticated relay attacks against the verification logic.
The operational impact of this flaw is severe because it undermines the fundamental guarantee of RA-TLS, which is ensuring that the attested enclave is indeed the one participating in the current communication channel. An attacker who has compromised or obtained an enclave TLS private key can exploit this weakness by intercepting a legitimate connection attempt and relaying its cryptographic quote to a different target connection where they hold the corresponding client credentials. Because the verification logic does not check that the quote matches the specific session parameters, such as the handshake transcript or ephemeral keys used during the TLS negotiation, it will accept the relayed quote as valid for the new context. Consequently, the application is tricked into establishing a secure channel with an attacker-terminated connection rather than the genuine attested enclave, effectively bypassing remote attestation protections and allowing man-in-the-middle attacks to proceed undetected.
This vulnerability aligns closely with CWE-327, which describes the use of a broken or risky cryptographic algorithm, specifically in this case, the failure to properly bind authentication data to the session context, leading to a lack of integrity verification for the communication channel. From an offensive security perspective, such techniques are consistent with ATT&CK technique T1557, Adversary-in-the-Middle, where attackers position themselves between two parties who believe they are directly communicating. The failure to bind the attestation quote to the TLS session parameters represents a critical design flaw in the authentication flow that allows credential theft and impersonation even when strong hardware-based security features like Intel SGX or AMD SEV are otherwise properly configured.
To mitigate this vulnerability, organizations must immediately upgrade their RA-TLS client utilities to version 0.5.0 or later, where the fix ensures that the quote ReportData is cryptographically bound to all relevant session-specific data. This includes incorporating hashes of the TLS handshake messages into the attestation payload so that any modification or relaying of quotes results in verification failure. Additionally, developers should implement strict certificate pinning and ensure that their security architectures assume potential compromise of individual components by enforcing defense-in-depth strategies. Regular audits of cryptographic implementations against industry standards such as NIST SP 800-193 for platform firmware attestation can help identify similar binding flaws before they are exploited in production environments.