An attacker can exploit the vulnerability by sending a malformed protocol-specific Telnet command while establishing a connection to the affected device, because of a flaw in how the protocol fails to properly process some commands.
Cisco said that there are “no workarounds” to address the vulnerability, but it said that disabling Telnet would “eliminate” some risks.
Source: Hundreds of Cisco switches vulnerable to flaw found in WikiLeaks files | ZDNet