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I'm trying to connect via SSH to a remote SUSE Linux Enterprise Server 11 from a Windows 10 Computer.

When using Putty 0,73, it works without problems. But using WSL2/Debian I get always refused.

On the Linux Machine, when I open the /var/log/messages file I can see the following line appearing everytime I try to access using WSL2:

Feb 8 12:46:31 remotecomputername sshd[13536]: fatal: buffer_put_cstring: s == NULL [preauth]

On WSL I simply get a Connection closed error:

$ ssh root@ip-of-remote-linux
Connection closed by ip-of-remote-linux port 22

Any ideas what is the problem between the two computers?

Ñhosko
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  • SLES 11 is many years past end of life. It is likely that this problem cannot be solved, as it should have been upgraded or decommissioned several years ago. It is probably no longer possible to delay this upgrade. – Michael Hampton Feb 08 '21 at 13:20
  • [This answer](https://serverfault.com/a/1065408/26694) might provide a solution: install and use `openssh-client-ssh1` – Amir Jun 02 '21 at 14:30

2 Answers2

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I don't have an answer for the putty part of the problem but from Linux, adding "-c aes256-cbc" to the command line might work. It does for me going from CentOS 8.1 -> SLES11. I have many ancient SLES servers I still need to access in spite of the fact that they "should have" been replaced.

Tom Guest
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  • I can confirm that adding "-c aes256-cbc" to my ssh makes the connection to work as expected. Thanks for the work-around. – Ñhosko Jun 07 '21 at 11:07
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Debian (and others) deprecated a bunch of cryptos that were deemed unsafe some years ago. I suspect this is why you can't login. I don't know if Putty ever did this.

Fredrik
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