Exposed services · Telnet

Is Telnet on port 23 still a risk in 2026?

Yes.

Last read from the sources at the foot of this page.

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01

What is Telnet?

Telnet is a decades-old way to type commands on a router, printer, camera or server from somewhere else. It listens on port 23.

It often stays switched on in older equipment because nobody turned it off.

02

Why does it matter now?

GNU InetUtils Argument Injection Vulnerability 2026-01-26 GNU InetUtils contains an argument injection vulnerability in telnetd that could allow for remote authentication bypass via a "-f root" value for the USER environment variable.

CISA added a flaw in the GNU InetUtils Telnet server to its catalog of exploited flaws on 26 January 2026. CISA says the flaw could let a remote attacker get past the sign-in altogether.

A device that answers Telnet from the internet invites that kind of attack.

03

What do I do about it?

  1. Find which device answers on port 23 and turn Telnet off in its settings.
  2. Remove any port forwarding rule for port 23 in your router or firewall.
  3. Where remote management is needed, use SSH over a VPN instead.
  4. Update the device's software, or replace equipment that no longer gets updates.
Sources

Where does this come from?

Related
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