Postorius through 1.3.13 does not escape HTML in the message subject when rendering it in the Held messages pop-up, as exploited in the wild in May 2026.

The remote Ubuntu 18.04 LTS / 20.04 LTS / 22.04 LTS / 24.04 LTS / 25.10 / 26.04 LTS host has packages installed that are affected by a vulnerability as referenced in the USN-8323-1 advisory.

    It was discovered that Postorius did not properly escape HTML in message subjects when rendering the Held     messages pop-up. An attacker could possibly use this issue to inject arbitrary HTML, resulting in exposure     of sensitive information.

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 remote Debian 11 host has a package installed that is affected by a vulnerability as referenced in the dla-4600 advisory.

    -------------------------------------------------------------------------     Debian LTS Advisory DLA-4600-1                debian-lts@lists.debian.org     https://www.debian.org/lts/security/                       Daniel Leidert     May 25, 2026                                  https://wiki.debian.org/LTS
    -------------------------------------------------------------------------

    Package        : postorius     Version        : 1.3.4-2+deb11u2     CVE ID         : CVE-2026-44742     Debian Bug     : 1136003

    A vulnerability has been discovered in postorius, a web user interface     to access GNU Mailman3.

    CVE-2026-44742

       If an email is sent to a mailing list with a subject containing HTML        code and placed in Held messages, the HTML code is rendered without        escaping in the title of the Held messages pop-up leading to a        Cross-site Scripting (XSS) vulnerability..

    For Debian 11 bullseye, this problem has been fixed in version     1.3.4-2+deb11u2.

    We recommend that you upgrade your postorius packages.

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

    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: This is a digitally signed message part

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 version of FreeBSD installed on the remote host is prior to tested version. It is, therefore, affected by a vulnerability as referenced in the 5b3b7f60-4de9-11f1-873e-0f64d023d0c7 advisory.

    NIST reports:

            Postorius through 1.3.13 does not escape HTML in the             message subject when rendering it in the Held messages             pop-up, as exploited in the wild in May 2026.


Tenable has extracted the preceding description block directly from the FreeBSD 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 a package installed that is affected by a vulnerability as referenced in the dsa-6257 advisory.

    - -------------------------------------------------------------------------     Debian Security Advisory DSA-6257-1                   security@debian.org     https://www.debian.org/security/                       Moritz Muehlenhoff     May 08, 2026                          https://www.debian.org/security/faq
    - -------------------------------------------------------------------------

    Package        : postorius     CVE ID         : CVE-2026-44742

    A cross-site scripting vulnerability was discovered in Postorius, the     administrative web frontend for Mailman 3.

    For the oldstable distribution (bookworm), this problem has been fixed     in version 1.3.8-3+deb12u1.

    For the stable distribution (trixie), this problem has been fixed in     version 1.3.13-1+deb13u1.

    We recommend that you upgrade your postorius packages.

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

    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.

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

  - Postorius through 1.3.13 does not escape HTML in the message subject when rendering it in the Held     messages pop-up, as exploited in the wild in May 2026. (CVE-2026-44742)

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

ID	Name	Product	Family	Severity
317477	Ubuntu 18.04 LTS / 20.04 LTS / 22.04 LTS / 24.04 LTS / 25.10 / 26.04 LTS : Postorius vulnerability (USN-8323-1)	Nessus	Ubuntu Local Security Checks	medium
316849	Debian dla-4600 : python3-django-postorius - security update	Nessus	Debian Local Security Checks	medium
314370	FreeBSD : postorius -- XSS (5b3b7f60-4de9-11f1-873e-0f64d023d0c7)	Nessus	FreeBSD Local Security Checks	medium
313419	Debian dsa-6257 : python3-django-postorius - security update	Nessus	Debian Local Security Checks	medium
313182	Linux Distros Unpatched Vulnerability : CVE-2026-44742	Nessus	Misc.	medium

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