telnetd in GNU Inetutils through 2.7 allows remote authentication bypass via a "-f root" value for the USER environment variable.

Exploitation attempts have been observed for this telnet flaw. Immediate patching is recommended as well as restricting access to the service to trusted clients

The Linux/Unix host has one or more packages installed that are impacted by a vulnerability without a vendor supplied patch available.

  - telnetd in GNU Inetutils through 2.7 allows remote authentication bypass via a -f root value for the     USER environment variable. (CVE-2026-24061)

Note that Nessus relies on the presence of the package as reported by the vendor.

The remote Ubuntu 22.04 LTS / 24.04 LTS / 25.10 host has packages installed that are affected by a vulnerability as referenced in the USN-7992-1 advisory.

    Kyu Neushwaistein discovered that telnetd in Inetutils incorrectly handled certain environment variables.
    A remote attacker could use this issue to bypass authentication and open a session as an administrator.

Tenable has extracted the preceding description block directly from the Ubuntu security advisory.

Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version number.

The telnetd server in GNU Inetutils passes the value of the USER environment variable received from a client to the system's login(1) program without sanitization.

An unauthenticated, remote attacker can set this value to '-f root' and bypass normal authentication, resulting in a root login.

The remote host is affected by the vulnerability described in GLSA-202601-01 (inetutils: Remote Code Execution)

    The telnetd server invokes /usr/bin/login (normally running as root) passing the value of the USER     environment variable received from the client as the last parameter.

    If the client supply a carefully crafted USER environment value being the string -f root, and passes the     telnet(1) -a or --login parameter to send this USER environment to the server, the client will be     automatically logged in as root bypassing normal authentication processes.

    This happens because the telnetd server do not sanitize the USER environment variable before passing it on     to login(1), and login(1) uses the -f parameter to by-pass normal authentication.

Tenable has extracted the preceding description block directly from the Gentoo Linux security advisory.

Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version number.

The remote Debian 11 host has packages installed that are affected by a vulnerability as referenced in the dla-4453 advisory.

    -------------------------------------------------------------------------     Debian LTS Advisory DLA-4453-1                debian-lts@lists.debian.org     https://www.debian.org/lts/security/                   Andreas Henriksson     January 25, 2026                              https://wiki.debian.org/LTS
    -------------------------------------------------------------------------

    Package        : inetutils     Version        : 2:2.0-1+deb11u3     CVE ID         : CVE-2026-24061     Debian Bug     : 1126047

    Kyu Neushwaistein aka Carlos Cortes Alvarez found that inetutils,     a collection of common network programs, was vulnerable to an authentication     bypass problem in telnetd, which could lead to remote root shell access (if     telnetd is enabled and exposed).

    As described also in the GNU InetUtils security advisory, it is not     recommended to run telnetd server at all. At a minimum, restrict network     access to the telnet port to trusted clients only. There is after all no     encryption built into the telnet protocol, so authentication details would     be sent in plain text over the network (which thus needs to be trusted).

    For more details see the GNU InetUtils Security Advisory:
    https://lists.gnu.org/archive/html/bug-inetutils/2026-01/msg00004.html

    For Debian 11 bullseye, this problem has been fixed in version     2:2.0-1+deb11u3.

    We recommend that you upgrade your inetutils packages.

    For the detailed security status of inetutils please refer to     its security tracker page at:
    https://security-tracker.debian.org/tracker/inetutils

    Further information about Debian LTS security advisories, how to apply     these updates to your system and frequently asked questions can be     found at: https://wiki.debian.org/LTS     Attachment:
    signature.asc     Description: PGP signature

Tenable has extracted the preceding description block directly from the Debian security advisory.

Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version number.

The remote Debian 12 / 13 host has packages installed that are affected by a vulnerability as referenced in the dsa-6106 advisory.

    - -------------------------------------------------------------------------     Debian Security Advisory DSA-6106-1                   security@debian.org     https://www.debian.org/security/                     Salvatore Bonaccorso     January 22, 2026                      https://www.debian.org/security/faq
    - -------------------------------------------------------------------------

    Package        : inetutils     CVE ID         : CVE-2026-24061     Debian Bug     : 1126047

    Kyu Neushwaistein discovered that telnetd from inetutils does not     sanitize the USER environment variable before passing it on to login. A     remote attacker can take advantage of this flaw to login as root,     bypassing normal authentication processes.

    For the oldstable distribution (bookworm), this problem has been fixed     in version 2:2.4-2+deb12u2.

    For the stable distribution (trixie), this problem has been fixed in     version 2:2.6-3+deb13u1.

    We recommend that you upgrade your inetutils packages.

    For the detailed security status of inetutils please refer to its     security tracker page at:
    https://security-tracker.debian.org/tracker/inetutils

    Further information about Debian Security Advisories, how to apply     these updates to your system and frequently asked questions can be     found at: https://www.debian.org/security/

    Mailing list: debian-security-announce@lists.debian.org

Tenable has extracted the preceding description block directly from the Debian security advisory.

Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version number.

ID	Name	Product	Family	Severity
297689	Linux Distros Unpatched Vulnerability : CVE-2026-24061	Nessus	Misc.	critical
297660	Ubuntu 22.04 LTS / 24.04 LTS / 25.10 : Inetutils vulnerability (USN-7992-1)	Nessus	Ubuntu Local Security Checks	critical
297230	GNU Inetutils telnetd Remote Authentication Bypass (CVE-2026-24061)	Nessus	Misc.	critical
296594	GLSA-202601-01 : inetutils: Remote Code Execution	Nessus	Gentoo Local Security Checks	critical
296511	Debian dla-4453 : inetutils - security update	Nessus	Debian Local Security Checks	critical
294968	Debian dsa-6106 : inetutils - security update	Nessus	Debian Local Security Checks	critical

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