Telnet Servers Exposed!

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 Security researchers have recently identified around 800,000 Telnet servers exposed to the internet, many of them running vulnerable versions of GNU InetUtils telnetd. This exposure is dangerous because a critical authentication bypass vulnerability (CVE‑2026‑24061) allows attackers to log in as root without a password.

  • Nearly 800,000 IPs show Telnet fingerprints worldwide. [techradar.com]
  • The flaw affects GNU InetUtils 1.9.3 through 2.7 and is fixed in version 2.8. [bleepingcomputer.com]
  • Attackers can exploit it simply by injecting USER=-f root during connection, which forces a root login. [csoonline.com]
  • Exploitation began within 24 hours of patch release. GreyNoise observed 60 malicious sessions from 18 IPs, targeting root accounts in 83% of attempts. [techradar.com]

Why exposed Telnet is dangerous

Using Telnet today is unsafe for two main reasons:

1. Telnet transmits everything in plaintext

Credentials and session data can be easily captured by anyone sniffing network traffic. 

2. The new vulnerability allows full takeover

This flaw enables:

  • Unauthenticated root shell access
  • Remote code execution (RCE)
  • Malware deployment attempts (some attackers tried installing Python-based malware) 

Some devices vulnerable:

  • Legacy Linux installations
  • Routers and IoT devices
  • Embedded systems running InetUtils for a decade or more without updates

What you should do if you have (or suspect) exposed Telnet

Immediate mitigations

  • Disable telnetd entirely if possible. 
  • Block TCP port 23 on all firewalls. 
  • If disabling is impossible, restrict access to trusted internal IPs only.

Permanent fix

  • Upgrade to GNU InetUtils 2.8 or later, which patches CVE‑2026‑24061.

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