ssh は "sshd[xxxx]: ssh_dispatch_run_fatal:Connection from x.x.x.x port xxxxx: DH GEX group out of range [preauth]" エラーで失敗する

Issue

• Windows クライアントから RHEL-8 への SSH 接続試行が次の sshd エラーで失敗します。

  sshd[31281]: ssh_dispatch_run_fatal: Connection from x.x.x.x port 52266: DH GEX group out of range [preauth]
  

• Windows クライアント側のエラー:

  [sshexec] Connecting to example.com:22
  [sshexec] Connecting to example.com port 22
  [sshexec] Connection established
  [sshexec] Remote version string: SSH-2.0-OpenSSH_8.0
  [sshexec] Local version string: SSH-2.0-JSCH-0.1.39
  [sshexec] CheckCiphers: aes256-cbc,aes192-cbc,aes128-cbc
  [sshexec] SSH_MSG_KEXINIT sent
  [sshexec] SSH_MSG_KEXINIT received
  [sshexec] kex: server->client aes128-cbc hmac-sha1 none
  [sshexec] kex: client->server aes128-cbc hmac-sha1 none
  [sshexec] SSH_MSG_KEX_DH_GEX_REQUEST(1024<1024<1024) sent
  [sshexec] expecting SSH_MSG_KEX_DH_GEX_GROUP
  [sshexec] Disconnecting from example.com port 22
  [sshexec] Caught exception: Session.connect: java.io.IOException: End of IO Stream Read