A backdoor in the SSH management portion of Cisco's "Cisco Nexus 9000 Series Application Centric Infrastructure (ACI) Mode Switch Software" has been documented (archived). This particular incarnation of the hole has been patched by Cisco after the whistle was blown. The hole involves a default root SSH keypair which could be used by anyone connecting over IPv6 to login as root. This is not the first Cisco NOBUS backdoor to be burned after the definition of "us" capable of using the backdoor expanded.