The client side in OpenSSH 5.7 through 8.4 has an Observable Discrepancy leading to an information leak in the algorithm negotiation. This allows man-in-the-middle attackers to target initial connection attempts (where no host key for the server has been cached by the client). NOTE: some reports state that 8.5 and 8.6 are also affected.
https://security.netapp.com/advisory/ntap-20200709-0004/
https://security.gentoo.org/glsa/202105-35
https://github.com/ssh-mitm/ssh-mitm/blob/master/ssh_proxy_server/plugins/session/cve202014145.py
https://github.com/openssh/openssh-portable/compare/V_8_3_P1...V_8_4_P1
https://docs.ssh-mitm.at/CVE-2020-14145.html
https://anongit.mindrot.org/openssh.git/commit/?id=b3855ff053f5078ec3d3c653cdaedefaa5fc362d