Thanks for your post.

I have added this issue to the tracker:
Issue 2246 – Mitigations for SSH protocol "Terrapin" vulnerability

Support for "kex-strict" fixes the newly discovered "Terrapin" SSH vulnerability.

See here:

• https://www.chiark.greenend.org.uk/~sgtatham/putty/changes.html
  
• https://terrapin-attack.com/
  
• https://nvd.nist.gov/vuln/detail/CVE-2023-48795