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I'm using the current version of putty 0.66 and I keep on getting this error

Disconnected: Server protocol violation: unexpected SSH2_MSG_UNIMPLEMENTED packet

when I try to connect to a ssh tunnel. Here's my event log,

 Event Log: Looking up host "216.186.209.69"

Event Log: Connecting to 216.186.209.69 port 22

Event Log: We claim version: SSH-2.0-PuTTY_Release_0.66

Event Log: Server version: SSH-2.0-ROSSSH

Event Log: Using SSH protocol version 2

Outgoing packet #0x0, type 20 / 0x14 (SSH2_MSG_KEXINIT)


Incoming packet #0x0, type 20 / 0x14 (SSH2_MSG_KEXINIT)
                    ..........
Event Log: Doing Diffie-Hellman group exchange

Outgoing packet #0x1, type 34 / 0x22 (SSH2_MSG_KEX_DH_GEX_REQUEST)
            .......... .
Incoming packet #0x1, type 31 / 0x1f (SSH2_MSG_KEX_DH_GEX_GROUP)
                    ..........
Event Log: Doing Diffie-Hellman key exchange with hash SHA-256

Outgoing packet #0x2, type 32 / 0x20 (SSH2_MSG_KEX_DH_GEX_INIT)
                                    Il..
Incoming packet #0x2, type 33 / 0x21 (SSH2_MSG_KEX_DH_GEX_REPLY)

                                  d-%..
Event Log: Host key fingerprint is:

Event Log: ssh-dss 1024 2b:2f:13:27:36:a5:1b:02:e5:1a:fe:04:cf:90:ae:10

Outgoing packet #0x3, type 21 / 0x15 (SSH2_MSG_NEWKEYS)

Event Log: Initialised AES-256 CBC client->server encryption

Event Log: Initialised HMAC-SHA1 client->server MAC algorithm

Incoming packet #0x3, type 21 / 0x15 (SSH2_MSG_NEWKEYS)

Event Log: Initialised AES-256 CBC server->client encryption

Event Log: Initialised HMAC-SHA1 server->client MAC algorithm

Outgoing packet #0x4, type 2 / 0x02 (SSH2_MSG_IGNORE)
                                       ....
Outgoing packet #0x5, type 5 / 0x05 (SSH2_MSG_SERVICE_REQUEST)

Incoming packet #0x4, type 6 / 0x06 (SSH2_MSG_SERVICE_ACCEPT)

Outgoing packet #0x6, type 2 / 0x02 (SSH2_MSG_IGNORE)
  0                                     
Outgoing packet #0x7, type 50 / 0x32 (SSH2_MSG_USERAUTH_REQUEST)

Incoming packet #0x5, type 52 / 0x34 (SSH2_MSG_USERAUTH_SUCCESS)

Event Log: Access granted

Event Log: Opening session as main channel

Outgoing packet #0x8, type 2 / 0x02 (SSH2_MSG_IGNORE)

Outgoing packet #0x9, type 90 / 0x5a (SSH2_MSG_CHANNEL_OPEN)

Incoming packet #0x6, type 91 / 0x5b (SSH2_MSG_CHANNEL_OPEN_CONFIRMATION)

Event Log: Opened main channel

Event Log: Local port 8080 SOCKS dynamic forwarding

Outgoing packet #0xa, type 2 / 0x02 (SSH2_MSG_IGNORE)

Outgoing packet #0xb, type 98 / 0x62 (SSH2_MSG_CHANNEL_REQUEST)

Outgoing packet #0xc, type 2 / 0x02 (SSH2_MSG_IGNORE)

Outgoing packet #0xd, type 98 / 0x62 (SSH2_MSG_CHANNEL_REQUEST)

Incoming packet #0x7, type 99 / 0x63 (SSH2_MSG_CHANNEL_SUCCESS)

Event Log: Allocated pty (ospeed 38400bps, ispeed 38400bps)

Incoming packet #0x8, type 99 / 0x63 (SSH2_MSG_CHANNEL_SUCCESS)

Event Log: Started a shell/command

Incoming packet #0x9, type 94 / 0x5e (SSH2_MSG_CHANNEL_DATA)

Incoming packet #0xa, type 94 / 0x5e (SSH2_MSG_CHANNEL_DATA)

Incoming packet #0xb, type 94 / 0x5e (SSH2_MSG_CHANNEL_DATA)

Outgoing packet #0xe, type 2 / 0x02 (SSH2_MSG_IGNORE)
                                       ....
Outgoing packet #0xf, type 94 / 0x5e (SSH2_MSG_CHANNEL_DATA)

Outgoing packet #0x10, type 2 / 0x02 (SSH2_MSG_IGNORE)

Outgoing packet #0x11, type 94 / 0x5e (SSH2_MSG_CHANNEL_DATA)

Outgoing packet #0x12, type 2 / 0x02 (SSH2_MSG_IGNORE)
....

Outgoing packet #0x13, type 94 / 0x5e (SSH2_MSG_CHANNEL_DATA)
                       ........a
Event Log: Opening connection to www.bing.com:80 for forwarding from 127.0.0.1:49212

Outgoing packet #0x14, type 2 / 0x02 (SSH2_MSG_IGNORE)
                                    ....

Outgoing packet #0x15, type 90 / 0x5a (SSH2_MSG_CHANNEL_OPEN)


Event Log: Opening connection to www.bing.com:80 for forwarding from 127.0.0.1:49213

Outgoing packet #0x16, type 2 / 0x02 (SSH2_MSG_IGNORE)
                                     ....
Outgoing packet #0x17, type 90 / 0x5a (SSH2_MSG_CHANNEL_OPEN)
00     

Incoming packet #0xc, type 94 / 0x5e (SSH2_MSG_CHANNEL_DATA)

Incoming packet #0xd, type 91 / 0x5b (SSH2_MSG_CHANNEL_OPEN_CONFIRMATION)

Outgoing packet #0x18, type 2 / 0x02 (SSH2_MSG_IGNORE)

Outgoing packet #0x19, type 96 / 0x60 (SSH2_MSG_CHANNEL_EOF)
                                    ....
Incoming packet #0xe, type 91 / 0x5b (SSH2_MSG_CHANNEL_OPEN_CONFIRMATION)

Outgoing packet #0x1a, type 2 / 0x02 (SSH2_MSG_IGNORE)
                                       ....
Outgoing packet #0x1b, type 94 / 0x5e (SSH2_MSG_CHANNEL_DATA)

Incoming packet #0xf, type 98 / 0x62 (SSH2_MSG_CHANNEL_REQUEST)

Incoming packet #0x10, type 97 / 0x61 (SSH2_MSG_CHANNEL_CLOSE)

Outgoing packet #0x1c, type 2 / 0x02 (SSH2_MSG_IGNORE)

Event Log: Forwarded port closed
Incoming packet #0x11, type 94 / 0x5e (SSH2_MSG_CHANNEL_DATA)


Incoming packet #0x12, type 94 / 0x5e (SSH2_MSG_CHANNEL_DATA)

Outgoing packet #0x1e, type 2 / 0x02 (SSH2_MSG_IGNORE)

Outgoing packet #0x1f, type 98 / 0x62 (SSH2_MSG_CHANNEL_REQUEST)

Outgoing packet #0x20, type 2 / 0x02 (SSH2_MSG_IGNORE)

Outgoing packet #0x21, type 93 / 0x5d (SSH2_MSG_CHANNEL_WINDOW_ADJUST)

Incoming packet #0x13, type 94 / 0x5e (SSH2_MSG_CHANNEL_DATA)

Incoming packet #0x14, type 94 / 0x5e (SSH2_MSG_CHANNEL_DATA)

Outgoing packet #0x22, type 2 / 0x02 (SSH2_MSG_IGNORE)

Outgoing packet #0x23, type 98 / 0x62 (SSH2_MSG_CHANNEL_REQUEST)

Outgoing packet #0x24, type 2 / 0x02 (SSH2_MSG_IGNORE)

Outgoing packet #0x25, type 93 / 0x5d (SSH2_MSG_CHANNEL_WINDOW_ADJUST)

Incoming packet #0x15, type 3 / 0x03 (SSH2_MSG_UNIMPLEMENTED)

Outgoing packet #0x26, type 2 / 0x02 (SSH2_MSG_IGNORE)

Outgoing packet #0x27, type 1 / 0x01 (SSH2_MSG_DISCONNECT)


Event Log: Disconnected: Server protocol violation: unexpected SSH2_MSG_UNIMPLEMENTED packet
  • Change PuTTY logging to "SSH packets" + Anything useful in server log? – Martin Prikryl Dec 14 '15 at 7:10
  • 1
    You are probably dealing with server missing some features (SSH-2.0-ROSSSH) and Putty is not able to handle this message. But really, what are you trying to achieve? It looks pretty wild. – Jakuje Dec 14 '15 at 19:16
  • @MartinPrikryl i added new info of my ssh packets logs, hopes it helps – Kibbz Dec 15 '15 at 1:32
  • 1
    @Kibbz, may be your case was the same as I described in my answer below? I see it helped a lot of people - can you check it and select as right answer? – FlameStorm Dec 13 '16 at 19:03
38

For me the key was that the "Diffie-Hellman group exchange" key exchange algorithm was not implemented on the server (see Connection > SSH > KEX).

Moving this key exchange algorithm to the bottom of the list and making the algorithm "Diffie-Hellman group 14" first solved the problem for me.

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9

I got a similar error on 0.63 ... upgrading to 0.67 made it go away.

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  • @kibbz : you can make this answer as accepted, as this solves the desire issue. – Sumit Ramteke Dec 13 '16 at 10:40
0

I faced this error when remote disk was full. This is unexpected error.

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