Cisco is aware of active exploitation of a previously unknown vulnerability in the web UI feature of Cisco IOS XE Software when exposed to the internet or to untrusted networks. This vulnerability allows a remote, unauthenticated attacker to create an account on an affected system with privilege level 15 access. The attacker can then use that account to gain control of the affected system.
For steps to close the attack vector for this vulnerability, see the Recommendations section of this advisory
Cisco will provide updates on the status of this investigation and when a software patch is available.