A Catalyst 6K running the K9 software image may crash when an SSH client tries to connect. This problem is first found in Catalyst OS (CatOS) version 8.3(2).
The switch may crash while establishing an SSH connection to the client. The chances of this are very low.
This issue is documented in Cisco bug ID CSCef42764.
To resolve this issue, upgrade the CatOS to 8.3(4) or later. As an alternative, use Telnet or SSH version 1.0.