[Ufmrg] Re: [Seat] Comments on formal analysis of relay attacks in intra-handshake attestation (CVE-2026-33697)

[Muhammad Usama Sardar <[e-mail]>]

Hi Nathanael, all,

First, we have corrected the subject of this thread to /intra/-handshake 
attestation. As the title of our contribution [0,1] to the WG/RG 
suggests, that is exactly what our contribution is about. That is, CVE 
applies strictly to /intra/-handshake attestation and not to 
/post/-handshake attestation, for instance.

On 02.07.26 04:22, Nathanael Ritz wrote:

> I really don't think any further effort from me is necessary right now.

In the mean time, we have done further analysis. While we remain 
unconvinced of the relevance of your property for the purposes of 
/binding levels/, we appreciate your review and have acknowledged your 
efforts in the repo [2]. Thank you!

We also thank and acknowledge Songbo Bu for sharing his valuable 
insights [2]. In particular, we appreciate his question of the security 
property that hybrid (intra- + post-handshake attestation) can satisfy 
that post-handshake attestation alone cannot satisfy. We believe this is 
the right direction forward for the WG/RG. We also agree with him that 
security property should be independent of the draft.

Since IETF is volunteer work, nothing is necessary right now per se. 
Whenever time permits, we would be happy if you can formalize such a 
security property that Songbo proposed. This property would serve as a 
counter-example to our suggestion of Sec. 9 of the paper [0], and may 
help us and the WG absorb this additional complexity of intra-handshake 
attestation, given the demonstrated risk of high-severity and 
critical-severity vulnerabilities.

We also agree with Songbo that unnecessary code of intra-handshake 
attestation is not helpful even if it is optional. Intra-handshake 
attestation is one concrete addition in the TLS state machine; whether 
that specific path is taken or not in a specific execution is a 
different question.

===

In the mean time, we have practical proof-of-concept for reproducibility 
of exploits in intra-handshake attestation. A technical report on this 
is being prepared. It will be shared with the WG/RG when it is 
peer-reviewed and accepted.

===

We welcome any further feedback from other SEAT WG participants and 
formal methods experts in UFMRG.

Best regards,

Usama, Slava, and Jean-Marie


[0] 
https://www.researchgate.net/publication/408219182_Intra-handshakefail_CVE-2026-33697_High-severity_CVE_in_Attested_TLS 


[1] https://github.com/CCC-Attestation/formal-spec-KBS

[2] https://github.com/CCC-Attestation/formal-spec-KBS#acknowledgments