GNU InetUtils Argument Injection Vulnerability (CVE-2026-24061)

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.

Published Jan 21, 2026 · Updated May 29, 2026

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Why patchRisk explained in plain English

Worst-case scenarioIf unpatched

A remote attacker, without authentication, can achieve full data confidentiality loss, arbitrary modification of data, complete denial of service or system unavailability. Federal agencies are required to remediate by 2026-02-16 under CISA BOD 22-01.

How the attack worksNo clicks needed

This is a Software Vulnerability (CWE-88) (CWE-88) vulnerability in GNU InetUtils. telnetd in GNU Inetutils through 2.7 allows remote authentication bypass via a "-f root" value for the USER environment variable. Exploitation requires remote network access, low attack complexity, no authentication required, and no user interaction required.

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Malicious file

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Server compromised

Am I affected?Quick check

Probably yes if any of these apply:

●IT Security

●Running inetutils: 1.9.3 ≤ v ≤ 2.7; debian linux: 11.0

Real-world incidentsWhat we've seen

Active exploitation documented in the wild. Threat-research write-up: https://www.labs.greynoise.io/grimoire/2026-01-22-f-around-and-find-out-18-hours-of-unsolicited-houseguests/index.html

How to patch

Manual remediation steps

Apply the Vendor Patch

This vulnerability is in the CISA Known Exploited Vulnerabilities catalog — apply the vendor's security update as soon as possible.

CISA required action: Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.