Vulnerability resides in the Cluster Management Protocol (CMP) processing code in Cisco IOS / IOS XE software. If exploited, the flaw (CVE-2017-3881) could allow an unauthenticated, remote attacker to cause a reboot of an affected device or remotely execute malicious code. The vulnerability is in the default configuration of affected Cisco devices, even if the user doesn’t configure any cluster configuration commands. Until patches are available, Cisco recommends its users to disable the Telnet connection to the switch devices in favor of SSH.
Source: https://thehackernews.com/2017/03/cisco-network-switch-exploit.html