The C3-Series switches are heading to the end of support and there are no plans to modifying SSH on those solutions.
The OpenSSH Security Advisory provides the following information:
"
For most SSH usage scenarios, this attack has a very low likelihood of being carried out successfully - each attempt has a low probability of success and each failure will cause connection termination with a fatal error. It is therefore very unlikely for an interactive session to be usefully attacked using this protocol weakness: an attacker would expect around 11356 connection-killing attempts before they are likely to succeed."
Additional information is available at
http://www.openssh.com/txt/cbc.adv.
I hope it helps.
