•
10.2 ‘WARNING - POTENTIAL SECURITY BREACH!’
•
10.3 ‘The first cipher supported by the server is ... below the configured warning threshold’
•
10.4 ‘Server sent disconnect message type 2 (protocol error): "Too many authentication failures for root"’
•
10.5 ‘Out of memory’
•
10.6 ‘Internal error’, ‘Internal fault’, ‘Assertion failed’
•
10.7 ‘Unable to use this private key file’, ‘Couldn't load private key’, ‘Key is of wrong type’
•
10.8 ‘Server refused our public key’ or ‘Key refused’
•
10.9 ‘Access denied’, ‘Authentication refused’
•
10.10 ‘No supported authentication methods available’
•
10.11 ‘Incorrect CRC received on packet’ or ‘Incorrect MAC received on packet’
•
10.12 ‘Incoming packet was garbled on decryption’
•
10.13 ‘PuTTY X11 proxy: various errors’
•
10.14 ‘Network error: Software caused connection abort’
•
10.15 ‘Network error: Connection reset by peer’
•
10.16 ‘Network error: Connection refused’
•
10.17 ‘Network error: Connection timed out’
•
10.18 ‘Network error: Cannot assign requested address’
10.1 ‘The server's host key is not cached in the registry’
This error message occurs when PuTTY connects to a new SSH server. Every server identifies itself by means of a host key; once PuTTY knows the host key for a server, it will be able to detect if a malicious attacker redirects your connection to another machine.
If you see this message, it means that PuTTY has not seen this host key before, and has no way of knowing whether it is correct or not. You should attempt to verify the host key by other means, such as asking the machine's administrator.
If you see this message and you know that your installation of PuTTY has connected to the same server before, it may have been recently upgraded to SSH protocol version 2. SSH protocols 1 and 2 use separate host keys, so when you first use SSH-2 with a server you have only used SSH-1 with before, you will see this message again. You should verify the correctness of the key as before.
See
section 2.2
for more information on host keys.
10.2 ‘WARNING - POTENTIAL SECURITY BREACH!’
This message, followed by ‘The server's host key does not match the one PuTTY has cached in the registry’, means that PuTTY has connected to the SSH server before, knows what its host key should be, but has found a different one.
This may mean that a malicious attacker has replaced your server with a different one, or has redirected your network connection to their own machine. On the other hand, it may simply mean that the administrator of your server has accidentally changed the key while upgrading the SSH software; this shouldn't happen but it is unfortunately possible.
You should contact your server's administrator and see whether they expect the host key to have changed. If so, verify the new host key in the same way as you would if it was new.
See
section 2.2
for more information on host keys.
10.3 ‘The first cipher supported by the server is ... below the configured warning threshold’
This occurs when the SSH server does not offer any ciphers which you have configured PuTTY to consider strong enough. By default, PuTTY puts up this warning only for single-DES and Arcfour encryption.
See
section 4.20
for more information on this message.
10.4 ‘Server sent disconnect message type 2 (protocol error): "Too many authentication failures for root"’