Cisco issued a security bulletin on March 17, disclosing a remote code execution vulnerability in the Cluster Management Protocol function of IOS and IOS XE software, affecting over 300 Cisco switches and routers. Through this vulnerability, remote attackers can take complete control of a network device.
Cisco discovered the flaw while going through the WikiLeaks "Vault7" documents believed to have come from the CIA, suggesting that the flaw has been actively exploited. Naturally, every tech writer on the planet has rushed in to write doom and gloom stories of mass exploitation.
Slow down just a bit.
Those following long-standing best practices for securing infrastructure hardware are not at risk. The vulnerability can only be exploited through the Telnet protocol, and requires access to the management interface of a switch.
Telnet communicates with a remote device unencrypted - transmitting usernames and passwords, as well as commands and configuration details, in the clear where anyone listening can intercept them. All modern switches and routers support SSH, which serves the same purpose but with an encrypted connection.
Disable the Telnet service on your Cisco switches, restrict management to an isolated management network, and update the OS as soon as practical once Cisco issues a fix.
Carry on.
