SEAT M. U. Sardar Internet-Draft TU Dresden, Germany Intended status: Informational 31 July 2026 Expires: 1 February 2027 Intra-handshake Attestation Considered Harmful (CVE-2026-33697 of CVSS 7.5) draft-intra-handshake-fail-01 Abstract The draft aims to provide technical details of CVE-2026-33697, which is substantial technical evidence of how *intra*-handshake attestation fails in practice. Moreover, since continuous attestation is required, *intra*-handshake attestation adds *unnecessary complexity*. The results are backed by the research [Intra-handshake.fail] and the ProVerif artifacts [Intra-handshake.fail-repo] under Apache-2.0 license for reproducibility. About This Document This note is to be removed before publishing as an RFC. The latest revision of this draft can be found at https://muhammad- usama-sardar.github.io/intra-handshake-fail/draft-intra-handshake- fail.html. Status information for this document may be found at https://datatracker.ietf.org/doc/draft-intra-handshake-fail/. Source for this draft and an issue tracker can be found at https://github.com/muhammad-usama-sardar/intra-handshake-fail. Status of This Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at https://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." Sardar Expires 1 February 2027 [Page 1] Internet-Draft TODO - Abbreviation July 2026 This Internet-Draft will expire on 1 February 2027. Copyright Notice Copyright (c) 2026 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/ license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Revised BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Revised BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Conventions and Definitions . . . . . . . . . . . . . . . . . 4 3. Credits . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 4. Detailed Vulnerability Disclosure Timeline and Acknowledgements by Affected Vendors . . . . . . . . . . . . . . . . . . . 5 5. Comparison with Other Vulnerabilities in Confidential Computing Literature . . . . . . . . . . . . . . . . . . . . . . . 6 6. Affected Implementations . . . . . . . . . . . . . . . . . . 7 7. Binding Levels . . . . . . . . . . . . . . . . . . . . . . . 8 8. Correlation Goals . . . . . . . . . . . . . . . . . . . . . . 8 9. Main Results . . . . . . . . . . . . . . . . . . . . . . . . 8 9.1. Expected Results . . . . . . . . . . . . . . . . . . . . 9 10. Implications of Findings . . . . . . . . . . . . . . . . . . 10 10.1. Implications of Findings for IETF SEAT WG . . . . . . . 10 10.2. Implications of Findings for IETF LAKE WG . . . . . . . 11 10.3. Implications of Findings for IETF TLS WG . . . . . . . . 11 10.4. Implications of Findings for Agent2Agent . . . . . . . . 11 11. Technical Details . . . . . . . . . . . . . . . . . . . . . . 11 11.1. Tool . . . . . . . . . . . . . . . . . . . . . . . . . . 11 11.2. Modeling . . . . . . . . . . . . . . . . . . . . . . . . 11 11.3. Technical Report . . . . . . . . . . . . . . . . . . . . 12 11.4. Artifacts . . . . . . . . . . . . . . . . . . . . . . . 12 12. Media Coverage . . . . . . . . . . . . . . . . . . . . . . . 12 12.1. Security Researchers . . . . . . . . . . . . . . . . . . 14 12.2. Germany's BSI . . . . . . . . . . . . . . . . . . . . . 14 13. Reviews . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 13.1. Conference Reviews . . . . . . . . . . . . . . . . . . . 14 13.2. IETF/IRTF . . . . . . . . . . . . . . . . . . . . . . . 15 13.3. Researchers outside of IETF/IRTF . . . . . . . . . . . . 16 14. Security Considerations . . . . . . . . . . . . . . . . . . . 16 Sardar Expires 1 February 2027 [Page 2] Internet-Draft TODO - Abbreviation July 2026 15. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16 16. References . . . . . . . . . . . . . . . . . . . . . . . . . 16 16.1. Normative References . . . . . . . . . . . . . . . . . . 16 16.2. Informative References . . . . . . . . . . . . . . . . . 17 Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 17 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 19 1. Introduction This draft presents the formal specification and analysis of the candidate binding mechanisms for binding in intra-handshake attestation for standardization for attested TLS protocols: +===+===========+=========================================+=========================+ |No.|Binding |Used in |Artifacts | | |mechanism | | | +===+===========+=========================================+=========================+ |1. |Client’s |Meta's AI (https://ai.meta.com/static- |binder1 | | |TLS nonce |resource/private-processing-technical- |(https://github.com/ | | | |whitepaper) |muhammad-usama-sardar/ | | | | |intra- | | | | |handshake.fail/tree/main/| | | | |binder1) | +---+-----------+-----------------------------------------+-------------------------+ |2. |Client’s |- |binder2 | | |attestation| |(https://github.com/ | | |nonce | |muhammad-usama-sardar/ | | | | |intra- | | | | |handshake.fail/tree/main/| | | | |binder2) | +---+-----------+-----------------------------------------+-------------------------+ |3. |Early |- |binder3 | | |exporter | |(https://github.com/ | | | | |muhammad-usama-sardar/ | | | | |intra- | | | | |handshake.fail/tree/main/| | | | |binder3) | +---+-----------+-----------------------------------------+-------------------------+ |4. |Server’s |- |binder4 | | |public key | |(https://github.com/ | | | | |muhammad-usama-sardar/ | | | | |intra- | | | | |handshake.fail/tree/main/| | | | |binder4) | +---+-----------+-----------------------------------------+-------------------------+ |5. |Combination|- |binder5 | | |of #2 and | |(https://github.com/ | | |#3 | |muhammad-usama-sardar/ | Sardar Expires 1 February 2027 [Page 3] Internet-Draft TODO - Abbreviation July 2026 | | | |intra- | | | | |handshake.fail/tree/main/| | | | |binder5) | +---+-----------+-----------------------------------------+-------------------------+ |6. |Combination|Edgeless Systems Contrast |binder6 | | |of #2 and |(https://github.com/CCC- |(https://github.com/ | | |#4 |Attestation/meetings/blob/main/materials/|muhammad-usama-sardar/ | | | |MarkusRudy.contrast-atls-ccc- |intra- | | | |attestation.pdf); Cocos AI |handshake.fail/tree/main/| | | |(https://www.ultraviolet.rs/products/ |binder6) | | | |cocos-ai/); CCC Attestation SIG's adopted| | | | |project intra-handshake attestation | | | | |(https://github.com/ccc-attestation/ | | | | |attested-tls-poc) | | +---+-----------+-----------------------------------------+-------------------------+ |7. |Combination|draft-fossati-tls-attestation-06 |binder7 | | |of #2, #3, |(https://www.ietf.org/archive/id/draft- |(https://github.com/ | | |and #4 |fossati-tls-attestation-06.html) |muhammad-usama-sardar/ | | | | |intra- | | | | |handshake.fail/tree/main/| | | | |binder7) | +---+-----------+-----------------------------------------+-------------------------+ Table 1: Binding mechanisms, implementations and ProVerif artifacts We provide a formal proof of insecurity of all the above candidate binding mechanisms of intra-handshake attestation using the state-of-the-art tool ProVerif and propose a mitigation for the discovered security vulnerabilities. Our study reveals that it may not be possible to achieve strong application-traffic (level 3) binding using intra-handshake attestation alone. We responsibly disclosed the vulnerability in intra-handshake attestation -- as noted in security advisory (https://github.com/ultravioletrs/cocos/security/advisories/GHSA- vfgg-mvxx-mgg7) issued -- to the vendors, which resulted in [CVE-2026-33697] of CVSS 7.5. 2. Conventions and Definitions The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here. Sardar Expires 1 February 2027 [Page 4] Internet-Draft TODO - Abbreviation July 2026 3. Credits We discovered the vulnerability jointly with *Viacheslav Dubeyko* and *Jean-Marie Jacquet*. 4. Detailed Vulnerability Disclosure Timeline and Acknowledgements by Affected Vendors +============================================================================+======+ |Event |Date | +============================================================================+======+ |Our initial responsible disclosure to vendor |07 | | |Oct, | | |2025 | +----------------------------------------------------------------------------+------+ |Acknowledgement by vendor |14 | | |Dec, | | |2025 | +----------------------------------------------------------------------------+------+ |Information to the IETF (https://mailarchive.ietf.org/arch/msg/ |11 | |rats/6gbqx0XY8WYrH3Mx4vO8n2-uKgY/) |Jan, | | |2026 | +----------------------------------------------------------------------------+------+ |Public announcement |27 | |(https://web.archive.org/web/20260227160554/https://www.ultraviolet.rs/blog/|Feb, | |tee-tls-privacy/) by vendor |2026 | +----------------------------------------------------------------------------+------+ |Cocos AI published security advisory |23 | |(https://github.com/ultravioletrs/cocos/security/advisories/GHSA-vfgg-mvxx- |March,| |mgg7) [*Severity = HIGH (CVSS 7.8)*] |2026 | +----------------------------------------------------------------------------+------+ |CVE (CVE-2026-33697 (https://www.cve.org/CVERecord?id=CVE-2026-33697)) |26 | |published [*Severity = HIGH (CVSS 7.5)*] |March,| | |2026 | +----------------------------------------------------------------------------+------+ |CCC implementation (https://github.com/ccc-attestation/attested-tls-poc) |17 | |declared vulnerable to relay attacks (https://github.com/CCC-Attestation/ |July, | |attested-tls-poc/pull/58) |2026 | +----------------------------------------------------------------------------+------+ |Vulnerable CCC implementation repo (https://github.com/ccc-attestation/ |22 | |attested-tls-poc) archived |July, | | |2026 | +----------------------------------------------------------------------------+------+ |Vulnerable draft draft-fossati-tls-attestation |23 | |(https://datatracker.ietf.org/doc/draft-fossati-tls-attestation/10/) |July, | |withdrawn by authors |2026 | +----------------------------------------------------------------------------+------+ |Edgeless Systems published security advisory |29 | Sardar Expires 1 February 2027 [Page 5] Internet-Draft TODO - Abbreviation July 2026 |(https://github.com/edgelesssys/contrast/security/advisories/GHSA-hjgc-jc5v-|July, | |fw7h) [*Severity = HIGH (CVSS 7.4)*] |2026 | +----------------------------------------------------------------------------+------+ Table 2: Detailed vulnerability disclosure timeline and acknowledgements 5. Comparison with Other Vulnerabilities in Confidential Computing Literature Severity is based on NIST metrics (https://nvd.nist.gov/vuln-metrics/ cvss). +==============================+=========================================+====+========+ |Vulnerability |CVE |CVSS|Severity| +==============================+=========================================+====+========+ |wiretap.fail |No CVE (Intel |- |None | |(https://wiretap.fail/files/ |(https://www.intel.com/content/www/us/en/| | | |wiretap.pdf) |security-center/announcement/intel- | | | | |security-announcement- | | | | |2025-10-28-001.html) and AMD | | | | |(https://www.intel.com/content/www/us/en/| | | | |security-center/announcement/intel- | | | | |security-announcement- | | | | |2025-10-28-001.html) announcements) | | | +------------------------------+-----------------------------------------+----+--------+ |TEE.fail |No CVE |- |None | |(https://tee.fail/files/ | | | | |paper.pdf) | | | | +------------------------------+-----------------------------------------+----+--------+ |TDXdown (https://dl.acm.org/ |Intel |2.5 |Low | |doi/10.1145/3658644.3690230) |(https://www.intel.com/content/www/us/en/| | | | |security-center/announcement/intel- | | | | |security-announcement- | | | | |2024-10-08-001.html) | | | +------------------------------+-----------------------------------------+----+--------+ |Staleus (https://xca- |CVE-2025-54509 (https://www.cve.org/ |4.0 |Medium | |attacks.github.io/staleus/ |CVERecord?id=CVE-2025-54509) | | | |staleus_usenix26.pdf) | | | | +------------------------------+-----------------------------------------+----+--------+ |BreakFAST (https://xca- |CVE-2025-61972 (https://www.cve.org/ |4.2 |Medium | |attacks.github.io/breakfast/ |CVERecord?id=CVE-2025-6197) | | | |breakfast_oakland26.pdf) | | | | +------------------------------+-----------------------------------------+----+--------+ |BadRAM (https://badram.eu/ |AMD (https://www.amd.com/en/resources/ |5.3 |Medium | |badram.pdf) |product-security/bulletin/amd-sb- | | | | |3015.html) | | | +------------------------------+-----------------------------------------+----+--------+ Sardar Expires 1 February 2027 [Page 6] Internet-Draft TODO - Abbreviation July 2026 |BreakFAST (https://xca- |CVE-2025-61971 (https://www.cve.org/ |5.9 |Medium | |attacks.github.io/breakfast/ |CVERecord?id=CVE-2025-61971) | | | |breakfast_oakland26.pdf) | | | | +------------------------------+-----------------------------------------+----+--------+ |Fabricked (https://xca- |CVE-2025-54510 (https://www.cve.org/ |5.9 |Medium | |attacks.github.io/fabricked/ |CVERecord?id=cve-2025-54510) | | | |fabricked_usenix26.pdf) | | | | +------------------------------+-----------------------------------------+----+--------+ |Intra-handshake.fail |CVE-2026-33697 (https://www.cve.org/ |7.5 |High | |(https://www.researchgate.net/|CVERecord?id=CVE-2026-33697) | | | |publication/408219182_Intra- | | | | |handshakefail_CVE-2026- | | | | |33697_High- | | | | |severity_CVE_in_Attested_TLS) | | | | +------------------------------+-----------------------------------------+----+--------+ Table 3: Comparison with other vulnerabilities in confidential computing literature The comparison of the above with CVSS *7.5* for [Intra-handshake.fail] indicates that attested TLS is not mature yet compared to the rest of the confidential computing stack, and is currently one of the weakest links in the ecosystem. Further formal analysis of *production* implementation of intra- handshake attestation has led to discovery of another class of attacks and will potentially lead to three CVEs (currently under _responsible_ disclosure) each with an expected *CVSS 9.1*. 6. Affected Implementations At least the following implementations are affected: * Meta's AI (https://ai.meta.com/static-resource/private-processing- technical-whitepaper): CVE-2026-33697 (https://www.cve.org/ CVERecord?id=CVE-2026-33697) [*Severity = HIGH (CVSS 7.5)*] * Cocos AI (https://github.com/ultravioletrs/cocos): security advisory (https://github.com/ultravioletrs/cocos/security/advisories/GHSA- vfgg-mvxx-mgg7) [*Severity = HIGH (CVSS 7.8)*] and CVE-2026-33697 (https://www.cve.org/CVERecord?id=CVE-2026-33697) [*Severity = HIGH (CVSS 7.5)*] * Edgeless Systems Contrast (https://github.com/edgelesssys/ contrast): security advisory (https://github.com/edgelesssys/contrast/security/advisories/GHSA- hjgc-jc5v-fw7h) [*Severity = HIGH (CVSS 7.4)*] Sardar Expires 1 February 2027 [Page 7] Internet-Draft TODO - Abbreviation July 2026 * CCC Attestation SIG's adopted project intra-handshake attestation (https://github.com/ccc-attestation/attested-tls-poc): declared vulnerable to relay attacks (https://github.com/CCC-Attestation/ attested-tls-poc/pull/58) and *archived* 7. Binding Levels 1. DH shared secret (gxy) used as shared secret between client and server 2. Handshake traffic key (htsc) used for encryption of handshake messages 3. Application traffic key (astc) used for encryption of application data 8. Correlation Goals We consider TLS Server as RATS Attester, which is typical in confidential computing. 1. Correlation of Evidence to a DH Shared Secret (G1) 2. Correlation of Evidence to Client’s Handshake Traffic Key (G2) 3. Correlation of Evidence to Client’s Application Traffic Key (G3) 9. Main Results * All analyzed binding mechanisms and the corresponding implementations of intra-handshake attestation are vulnerable to relay attacks. * Early exporter helps achieve level 1 binding. * Our proposed mechanism helps achieve level 2 binding. * It may not be possible to achieve level 3 in intra-handshake attestation alone without additional assumptions. Sardar Expires 1 February 2027 [Page 8] Internet-Draft TODO - Abbreviation July 2026 +====================+====================+===========+===========+ | Property | Mechanism #1,2,4,6 | Mechanism | Proposed | | | | #3,5,7 | mechanism | +====================+====================+===========+===========+ | G1 : Correlation | ❌ | ✅ | ✅ | | of Evidence to gxy | | | | +--------------------+--------------------+-----------+-----------+ | G2 : Correlation | ❌ | ❌ | ✅ | | of Evidence to kch | | | | +--------------------+--------------------+-----------+-----------+ | G3 : Correlation | ❌ | ❌ | ❌ | | of Evidence to kc | | | | +--------------------+--------------------+-----------+-----------+ Table 4: Main results 9.1. Expected Results +===+===========+=========================+==================================+ |No.|Binding |Artifacts |Expected results | | |mechanism | | | +===+===========+=========================+==================================+ |1. |Client’s |binder1 |binder1 (https://github.com/ | | |TLS nonce |(https://github.com/ |muhammad-usama-sardar/intra- | | | |muhammad-usama-sardar/ |handshake.fail/tree/main/binder1/ | | | |intra- |log.txt) | | | |handshake.fail/tree/main/| | | | |binder1/) | | +---+-----------+-------------------------+----------------------------------+ |2. |Client’s |binder2 |binder2 (https://github.com/ | | |attestation|(https://github.com/ |muhammad-usama-sardar/intra- | | |nonce |muhammad-usama-sardar/ |handshake.fail/tree/main/binder2/ | | | |intra- |log.txt) | | | |handshake.fail/tree/main/| | | | |binder2/) | | +---+-----------+-------------------------+----------------------------------+ |3. |Early |binder3 |binder3 (https://github.com/ | | |exporter |(https://github.com/ |muhammad-usama-sardar/intra- | | | |muhammad-usama-sardar/ |handshake.fail/tree/main/binder3/ | | | |intra- |log.txt) | | | |handshake.fail/tree/main/| | | | |binder3/) | | +---+-----------+-------------------------+----------------------------------+ |4. |Server’s |binder4 |binder4 (https://github.com/ | | |public key |(https://github.com/ |muhammad-usama-sardar/intra- | | | |muhammad-usama-sardar/ |handshake.fail/tree/main/binder4/ | | | |intra- |log.txt) | | | |handshake.fail/tree/main/| | Sardar Expires 1 February 2027 [Page 9] Internet-Draft TODO - Abbreviation July 2026 | | |binder4/) | | +---+-----------+-------------------------+----------------------------------+ |5. |Combination|binder5 |binder5 (https://github.com/ | | |of #2 and |(https://github.com/ |muhammad-usama-sardar/intra- | | |#3 |muhammad-usama-sardar/ |handshake.fail/tree/main/binder5/ | | | |intra- |log.txt) | | | |handshake.fail/tree/main/| | | | |binder5/) | | +---+-----------+-------------------------+----------------------------------+ |6. |Combination|binder6 |binder6 (https://github.com/ | | |of #2 and |(https://github.com/ |muhammad-usama-sardar/intra- | | |#4 |muhammad-usama-sardar/ |handshake.fail/tree/main/binder6/ | | | |intra- |log.txt) | | | |handshake.fail/tree/main/| | | | |binder6/) | | +---+-----------+-------------------------+----------------------------------+ |7. |Combination|binder7 |binder7 (https://github.com/ | | |of #2, #3, |(https://github.com/ |muhammad-usama-sardar/intra- | | |and #4 |muhammad-usama-sardar/ |handshake.fail/tree/main/binder7/ | | | |intra- |log.txt) | | | |handshake.fail/tree/main/| | | | |binder7/) | | +---+-----------+-------------------------+----------------------------------+ |8. |Proposed |proposal |proposal (https://github.com/ | | | |(https://github.com/ |muhammad-usama-sardar/intra- | | | |muhammad-usama-sardar/ |handshake.fail/tree/main/proposal/| | | |intra- |log.txt) | | | |handshake.fail/tree/main/| | | | |proposal/) | | +---+-----------+-------------------------+----------------------------------+ Table 5: Expected results 10. Implications of Findings 10.1. Implications of Findings for IETF SEAT WG * We believe post-handshake attestation alone, such as draft- fossati-seat-expat (https://datatracker.ietf.org/doc/draft- fossati-seat-expat/), can achieve level 3 binding. * The research suggests that recent hybrid proposals (combination of intra-handshake attestation and post-handshake attestation) draft- fossati-seat-early-attestation (https://datatracker.ietf.org/doc/ draft-fossati-seat-early-attestation/04/) and draft-ritz-seat- facts (https://datatracker.ietf.org/doc/draft-ritz-seat-facts/00/) may add *unnecessary complexity* of intra-handshake attestation without adding any security benefit compared to post-handshake Sardar Expires 1 February 2027 [Page 10] Internet-Draft TODO - Abbreviation July 2026 attestation alone, such as draft-fossati-seat-expat (https://datatracker.ietf.org/doc/draft-fossati-seat-expat/). We are not aware of any security property that hybrid proposals can achieve that post-handshake attestation alone cannot achieve. 10.2. Implications of Findings for IETF LAKE WG * Similar problems occur for lake-ra (https://datatracker.ietf.org/doc/draft-ietf-lake-ra/). 10.3. Implications of Findings for IETF TLS WG * Remote attestation _within_ the handshake is very dangerous, since to our knowledge, it is one of the highest scored vulnerabilities in confidential computing literature (see Section 5). Given the high-severity vulnerabilities, we recommend that the developers and maintainers of intra-handshake attestation MUST urgently move to post-handshake attestation. 10.4. Implications of Findings for Agent2Agent Intra-handshake attestation does more damage than protection for AI agents. 11. Technical Details 11.1. Tool We use state-of-the-art symbolic security analysis tool ProVerif (https://ieeexplore.ieee.org/document/9833653) for the specification of the protocols. 11.2. Modeling The formal model uses the fixed version of diversion attacks in intra-handshake attestation (https://github.com/CCC-Attestation/ formal-spec-id-crisis/tree/main/TLS-a/fix) from our previous work as the starting point to focus on relay attacks in intra-handshake attestation in this work. The rationale is that we consider it more useful to show the added value of this contribution to the community by using the fixed version of diversion attacks in intra-handshake attestation (https://github.com/CCC-Attestation/formal-spec-id- crisis/tree/main/TLS-a/fix) as the baseline, rather than showing the same diversion attacks from ID-Crisis paper (https://dl.acm.org/ doi/10.1145/3779208.3785387), and the discovered CVE ([CVE-2026-33697]) -- which the previous analysis could not find -- practically demonstrates the added value. This modeling choice makes Sardar Expires 1 February 2027 [Page 11] Internet-Draft TODO - Abbreviation July 2026 it clear that even with the diversion attacks fixed, high-severity relay attacks would still remain in intra-handshake attestation. 11.3. Technical Report Technical report is available at [Intra-handshake.fail]. It is accepted for publication at ESORICS 2026. 11.4. Artifacts Artifacts are available at [Intra-handshake.fail-repo] under Apache- 2.0 License. 12. Media Coverage Several media enthusiasts have covered the vulnerabilities to protect the community from the harm of intra-handshake attestation. * The Register (https://www.theregister.com/security/2026/07/04/ confidential-computings-trust-mechanism-is-broken-the-fix-may-not- exist/5266056) * (Japanese) BlackHatNewsTokyo (https://blackhatnews.tokyo/ archives/119915) * (Several languages) Hackernoon (https://hackernoon.com/attested- tls-was-supposed-to-be-the-last-trust-boundary-it-isnt-formal- methods-show-how) * Apple podcast (https://podcasts.apple.com/eg/podcast/attested-tls- was-supposed-to-be-the-last-trust/id1698517643?i=1000776623286) * Information Security News (https://meterpreter.org/attested-tls- vulnerability-cve-2026-33697/) * TheNextGenTechInsider (https://thenextgentechinsider.com/pulse/ critical-flaw-discovered-in-confidential-computing-attestation- protocols) * DailySecurityReview (https://dailysecurityreview.com/resources/ cve-2026-33697-attested-tls-relay-flaw-hits-whatsapp-cocos-ai/) * SC World (https://www.scworld.com/brief/confidential-computings- remote-attestation-protocol-may-have-fundamental-flaw) * 01 Quantum (https://blogs.groupware.org.uk/01-Quantum-Inc/the- handshake-that-cant-keep-its-promise-why-confidential-computings- flaw-changes-the-data-sovereignty-conversation/) Sardar Expires 1 February 2027 [Page 12] Internet-Draft TODO - Abbreviation July 2026 * (Russian) Security Lab (https://www.securitylab.ru/ news/574545.php) * (German) blogspan (https://www.blogspan.net/confidential- computing-attestierung-relay-luecke/) * (Chinese) Sina (https://finance.sina.cn/tech/2026-07-04/detail- inifscxt9953361.d.html) * data4biz (https://data4biz.com/articles/una-falla-rompe-la- fiducia-del-confidential-computing) * (Russian) ITSec (https://www.itsec.ru/news/issledovateli-nashli- kriticheskuyu-uyazvimost-v-attested-tls) * (Chinese) smzdm (https://post.smzdm.com/p/a82ol990/) * (Chinese) donews (https://www.donews.com/news/ detail/4/6621022.html) * (Chinese) ifeng (https://i.ifeng.com/c/8uUfy0PMmqE) * dugganusa (https://www.dugganusa.com/post/confidential-computing- s-whole-pitch-is-trust-the-proof-not-the-cloud-two-years-of- formal-verifi) * dugganusa repo (https://github.com/pduggusa/dugganusa- ietf/tree/main/cve-2026-33697-attestation) * spoitus (https://sploitus.com/exploit?id=92591A05-07BC-5015-BA3D- B1347B35D684) * lavx news (https://news.lavx.hu/article/attested-tls-research- exposes-a-weak-link-in-confidential-computing) * (Chinese) csdn (https://blog.csdn.net/weixin_42376192/ category_13096766.html) * osintsights (https://osintsights.com/confidential-computing-flaws- expose-trust-risks) * (Turkish) hardwaremania (https://hardwaremania.com/haber/ arastirma-attested-tls-confidential-computing-icin-zayif-kaliyor/) * akber (https://akber.com/sovereignty-in-the-cloud-is-an-illusion/) Sardar Expires 1 February 2027 [Page 13] Internet-Draft TODO - Abbreviation July 2026 * ad-hoc news (https://www.ad-hoc-news.de/wissenschaft/cloud- souveraenitaet-red-hat-startet-reifegrad-assessments- gegen/69691475) * AIMultiple (https://aimultiple.com/privacy-enhancing-technologies) If you have written an article on this and would like to be added here, please send us a PR or an email with the subject "media coverage of intra-handshake.fail" 12.1. Security Researchers Credible security researchers, such as the following, have attested to it. * Michael Pak (https://www.linkedin.com/posts/ michaelpak_confidential-computings-core-trust-mechanism-activity- 7479415537836376064-q-A4/) * Rodrigo Branco (https://www.linkedin.com/posts/rrbranco_one-more- evidence-that-there-is-no-such-a-share-7479582122366615552-X0A5/) * Bart Preneel (https://www.linkedin.com/posts/bart-preneel- 4451412_on-the-limits-of-confidential-computing-share- 7479549718294077440-wfi3/) 12.2. Germany's BSI Germany's Federal Office for Information Security (Bundesamt für Sicherheit in der Informationstechnik) has attested to it. Carina Hilt, deputy press spokesperson at BSI, told The Register (https://www.theregister.com/security/2026/07/04/confidential- computings-trust-mechanism-is-broken-the-fix-may-not-exist/5266056): CC alone cannot satisfy the requirements for digital sovereignty. dependencies on other services, such as identity and key management etc., are also not mitigated by CC. 13. Reviews 13.1. Conference Reviews [Intra-handshake.fail] has been peer-reviewed and accepted for publication at ESORICS 2026. Sardar Expires 1 February 2027 [Page 14] Internet-Draft TODO - Abbreviation July 2026 13.2. IETF/IRTF Several participants of the IETF/IRTF have attested to the results by independently verifying the code. Some of the participants have independently reproduced the results by developing their own formal models and a proof-of-concept implementation of the vulnerabilities. Some of the messages are mentioned below: * https://mailarchive.ietf.org/arch/msg/seat/ov8f-7cZKK5RZ- Mmjc6IhVSB-Fk/ (https://mailarchive.ietf.org/arch/msg/seat/ov8f- 7cZKK5RZ-Mmjc6IhVSB-Fk/) * https://mailarchive.ietf.org/arch/msg/seat/wb_Ys9MZd9u9oM2Bk- 8tv7fvXGg/ (https://mailarchive.ietf.org/arch/msg/seat/ wb_Ys9MZd9u9oM2Bk-8tv7fvXGg/) * https://mailarchive.ietf.org/arch/msg/seat/2uUuaD1DygjNDM4GT_- rYbwTiJk/ (https://mailarchive.ietf.org/arch/msg/ seat/2uUuaD1DygjNDM4GT_-rYbwTiJk/) * https://mailarchive.ietf.org/arch/msg/seat/2_aGylmFHoLmqN7BBcYVoH- rNJk/ (https://mailarchive.ietf.org/arch/msg/ seat/2_aGylmFHoLmqN7BBcYVoH-rNJk/) * https://mailarchive.ietf.org/arch/msg/seat/ VyifG8zP5aworb_S1NR9FEUEXW0/ (https://mailarchive.ietf.org/arch/msg/seat/ VyifG8zP5aworb_S1NR9FEUEXW0/) * https://mailarchive.ietf.org/arch/msg/seat/P_CYTycg0KG7cbKauFA- kVgX2jo/ (https://mailarchive.ietf.org/arch/msg/seat/ P_CYTycg0KG7cbKauFA-kVgX2jo/) * https://mailarchive.ietf.org/arch/msg/seat/ CYwvM75z6rTId2A3ZZvZJmHxOig/ (https://mailarchive.ietf.org/arch/msg/seat/ CYwvM75z6rTId2A3ZZvZJmHxOig/) * https://mailarchive.ietf.org/arch/msg/seat/ aFCo4BMRDSUynvN9AQJatPjnXag/ (https://mailarchive.ietf.org/arch/msg/seat/ aFCo4BMRDSUynvN9AQJatPjnXag/) * https://mailarchive.ietf.org/arch/msg/seat/ Q6Jmc58v0c1lDV3ujIY0AX_ofGA/ (https://mailarchive.ietf.org/arch/msg/seat/ Q6Jmc58v0c1lDV3ujIY0AX_ofGA/) Sardar Expires 1 February 2027 [Page 15] Internet-Draft TODO - Abbreviation July 2026 * https://mailarchive.ietf.org/arch/msg/cfrg/ U5YHd91lYjiqCTt9BZyVDNFeUpM/ (https://mailarchive.ietf.org/arch/msg/cfrg/ U5YHd91lYjiqCTt9BZyVDNFeUpM/) * https://mailarchive.ietf.org/arch/msg/seat/ u1HxYW9cJfVpi3Cf9q06ehwpYGE/ (https://mailarchive.ietf.org/arch/msg/seat/ u1HxYW9cJfVpi3Cf9q06ehwpYGE/) * https://mailarchive.ietf.org/arch/msg/seat/ beRzNNvwMifkRfJPfxecGoHpTDs/ (https://mailarchive.ietf.org/arch/msg/seat/ beRzNNvwMifkRfJPfxecGoHpTDs/) * https://mailarchive.ietf.org/arch/msg/seat/SG_A0016a- KMnXAkGtMUxokZmjc/ (https://mailarchive.ietf.org/arch/msg/seat/ SG_A0016a-KMnXAkGtMUxokZmjc/) * https://mailarchive.ietf.org/arch/msg/ seat/3w7-OW2CAVr0-QBz97eAMxB_nMI/ (https://mailarchive.ietf.org/arch/msg/ seat/3w7-OW2CAVr0-QBz97eAMxB_nMI/) * https://mailarchive.ietf.org/arch/msg/ ufmrg/29xFZX5C4oSGkpZAvXT_7YLW2Vc/ (https://mailarchive.ietf.org/arch/msg/ ufmrg/29xFZX5C4oSGkpZAvXT_7YLW2Vc/) 13.3. Researchers outside of IETF/IRTF Some researchers have approached us confirming the proof-of-concept of the vulnerabilities in intra-handshake attestation. More information will be added once their pre-prints/papers are public. 14. Security Considerations All of this document is about the *insecurity* of *intra*-handshake attestation. 15. IANA Considerations This document has no IANA actions. 16. References 16.1. Normative References Sardar Expires 1 February 2027 [Page 16] Internet-Draft TODO - Abbreviation July 2026 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, . 16.2. Informative References [CVE-2026-33697] CVE, "CoCoS attested TLS is vulnerable to relay attacks via extracted ephemeral TLS keys", March 2026, . [Intra-handshake.fail] Sardar, M. U., Dubeyko, V., and J.-M. Jacquet, "Intra- handshake.fail (CVE-2026-33697): High-severity CVE in Attested TLS", June 2026, . [Intra-handshake.fail-repo] Sardar, M. U., Dubeyko, V., and J.-M. Jacquet, "Intra- handshake.fail (CVE-2026-33697): High-severity CVE in Attested TLS", July 2026, . Acknowledgments We would like to thank our co-authors of paper for their valuable contributions: * Viacheslav Dubeyko * Jean-Marie Jacquet We gratefully acknowledge the following for insightful discussions on this work: * Eric Rescorla * Juho Forsén * Markus Rudy * Mariam Moustafa Sardar Expires 1 February 2027 [Page 17] Internet-Draft TODO - Abbreviation July 2026 * Bruno Blanchet * Steve Kremer * Tjaden Hess * Martin Thomson * Yuning Jiang * Pavel Nikonorov * Casey Wilson * Danko Miladinovic * Songbo Bu * John Preuß Mattsson * Werner Staub * Nathanael Ritz We also gratefully acknowledge the following who gave feedback on previous state-of-the-art (https://github.com/CCC-Attestation/formal- spec-id-crisis) that we utilize as the basis: * Tuomas Aura * Ionut Mihalcea * Thomas Fossati * Hannes Tschofenig * Yaron Sheffer * Laurence Lundblade * Giridhar Mandyam * Christopher Patton * Jonathan Hoyland * Richard Barnes Sardar Expires 1 February 2027 [Page 18] Internet-Draft TODO - Abbreviation July 2026 Several others at the IETF, IRTF, and CCC have contributed by providing feedback. We sincerely thank Karthikeyan Bhargavan, Bruno Blanchet, and Nadim Kobeissi for the foundational formal model of draft 20 of TLS 1.3 in their work (https://ieeexplore.ieee.org/document/7958594). Author's Address Muhammad Usama Sardar TU Dresden, Germany Email: muhammad_usama.sardar@tu-dresden.de Sardar Expires 1 February 2027 [Page 19]