Cisco published an advisory about multiple vulnerabilities in their IOS SSL implementation (http://www.cisco.com/en/US/products/products_security_advisory09186a0080847c49.shtml).
Several SSL messages (ClientHello, ChangeCipherSpec and Finished), when malformed, can cause Cisco IOS devices to crash.

Cisco said that this is only a DoS attack (no code execution seems to be possible) but as there are a lot of affected devices you should either install the patch or follow the workarounds (which are to disable the affected service(s)).

Thanks to Marc, CJ and Jim.