A vulnerability in the Secure Shell (SSH) server code of Cisco IOS Software and Cisco IOS XE Software could allow an authenticated, remote attacker to cause an affected device to reload. The vulnerability is due to an internal state not being represented correctly in the SSH state machine, which leads to an unexpected behavior. An attacker could exploit this vulnerability by creating an SSH connection to an affected device and using a specific traffic pattern that causes an error condition within that connection. A successful exploit could allow an attacker to cause the device to reload, resulting in a denial of service (DoS) condition.
https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-ssh-dos-Un22sd2A