An attacker might provide several incorrect login attempts at the telnet prompt until the account becomes locked out.
The account is unable to connect to the machine for the set lockout time.
NIST recommendation
If remote access is not available, this problem can be solved with physical access control.
How Messaging addresses the vulnerability
On Messaging systems, Telnet is disabled by default. SSH is the recommended protocol for remote access. In addition, physical access through a serial console is available on every Messaging server.