This is a new SSH protocol feature which mitigates this attack.
However, it is a cryptographic weakness to address. This affects extensions with security impact, such as server-sig-algs.
This can be used to sabotage SSH extension negotiation.
Terrapin - CVE-2023-48795: Researchers have identified an issue where all SSH connections which use the encryption algorithm ChaCha20-Poly1305, or any integrity algorithm of type encrypt-then-MAC, are vulnerable to packet sequence manipulation by an active attacker, if the attacker can intercept the network path.
