We use Putty to access our Linux servers from our windows workstations...

Today we created new servers with Ubuntu server 16.04 and installed openssh with tasksel (as allways).

When we try to connect remotely to our new Ubuntu server 16.04, we get a PuTTY Fatal Error...

Couldn't agree a client-to-server cipher (available: chacha20-poly1305@openssh.com,aes128-ctr,aes192-ctr,aes256-ctr,aes128-gcm@openssh.com,aes256-gcm@openssh.com)

PuTTY Fatal Error

Please tell me how to work around this problem ! Someone found a solution?

  • 2
    What version of putty are you using? May 3, 2016 at 14:19
  • 5
    As above - there's a chance you're using oldish version of Putty, which can't negotiate proper/newer ciphers. Download latest version of Putty and retry.
    – Jacek
    May 3, 2016 at 14:23

2 Answers 2


Yes, I had the same issue. Just upgrade Putty.

  • 1
    This might be indeed working, but it would be helpful if you could tell us to which version you've upgraded putty.
    – wie5Ooma
    Jun 22, 2016 at 14:29

Upgrade PuTTY: currently latest release (0.70), visit this link!

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