Linux Distros Unpatched Vulnerability : CVE-2026-78409

#%NASL_MIN_LEVEL 80900
##
# (C) Tenable, Inc.
##

include('compat.inc');

if (description)
{
  script_id(342606);
  script_version("1.2");
  script_set_attribute(attribute:"plugin_modification_date", value:"2026/09/04");

  script_cve_id("CVE-2026-78409");

  script_name(english:"Linux Distros Unpatched Vulnerability : CVE-2026-78409");

  script_set_attribute(attribute:"synopsis", value:
"The Linux/Unix host has one or more packages installed with a vulnerability that the vendor indicates will not be
patched.");
  script_set_attribute(attribute:"description", value:
"The Linux/Unix host has one or more packages installed that are impacted by a vulnerability without a vendor supplied
patch available.

  - The X-mount.subdir option uses a detached-tree fast path on Linux 6.15 and later and passes the configured
    subdirectory to open_tree() with AT_SYMLINK_NOFOLLOW. That flag does not stop intermediate symlink
    traversal or keep resolution inside the newly mounted filesystem. A local unprivileged user with an fstab-
    authorized X-mount.subdir entry can attach a host path at the intended mountpoint. (CVE-2026-78409)

Note that Nessus relies on the presence of the package as reported by the vendor.");
  script_set_attribute(attribute:"see_also", value:"https://security-tracker.debian.org/tracker/CVE-2026-78409");
  script_set_attribute(attribute:"solution", value:
"There is no known solution at this time.");
  script_set_attribute(attribute:"agent", value:"unix");
  script_set_cvss_base_vector("CVSS2#AV:L/AC:L/Au:N/C:P/I:P/A:N");
  script_set_cvss_temporal_vector("CVSS2#E:U/RL:U/RC:C");
  script_set_cvss3_base_vector("CVSS:3.0/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H");
  script_set_cvss3_temporal_vector("CVSS:3.0/E:U/RL:U/RC:C");
  script_set_attribute(attribute:"cvss_score_source", value:"CVE-2026-78409");

  script_set_attribute(attribute:"exploitability_ease", value:"No known exploits are available");
  script_set_attribute(attribute:"exploit_available", value:"false");
  script_set_attribute(attribute:"vendor_unpatched", value:"true");

  script_set_attribute(attribute:"vuln_publication_date", value:"2026/09/02");
  script_set_attribute(attribute:"plugin_publication_date", value:"2026/09/03");

  script_set_attribute(attribute:"plugin_type", value:"local");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:debian:debian_linux:12.0");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:debian:debian_linux:13.0");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:debian:debian_linux:14.0");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:debian:debian_linux:util-linux");
  script_set_attribute(attribute:"generated_plugin", value:"current");
  script_end_attributes();

  script_category(ACT_GATHER_INFO);
  script_family(english:"Misc.");

  script_copyright(english:"This script is Copyright (C) 2026 and is owned by Tenable, Inc. or an Affiliate thereof.");

  script_dependencies("ssh_get_info2.nasl", "set_linux_os_id.nasl");
  script_require_keys("Host/cpu", "Host/local_checks_enabled", "global_settings/vendor_unpatched", "Host/OS/identifier");
  script_require_ports("Host/OS/Debian Linux-12", "Host/OS/Debian Linux-13", "Host/OS/Debian Linux-14");

  exit(0);
}

if (!get_kb_item("global_settings/vendor_unpatched")) exit(0, "Unpatched Vulnerabilities Detection not active.");
if (!get_kb_item("Host/local_checks_enabled")) audit(AUDIT_LOCAL_CHECKS_NOT_ENABLED);
if (empty_or_null(get_one_kb_item("Host/Debian/dpkg-l"))) audit(AUDIT_PACKAGE_LIST_MISSING);

include('linux_unpatched.inc');

var distro_constraints_array = {
  "Debian Linux-12": {
    "package_manager": "dpkg-l",
    "constraints": [
      {
        "release": "12",
        "pkgs": [
          {"reference": "bsdextrautils"},
          {"reference": "bsdutils"},
          {"reference": "eject"},
          {"reference": "eject-udeb"},
          {"reference": "fdisk"},
          {"reference": "fdisk-udeb"},
          {"reference": "libblkid-dev"},
          {"reference": "libblkid1"},
          {"reference": "libblkid1-udeb"},
          {"reference": "libfdisk-dev"},
          {"reference": "libfdisk1"},
          {"reference": "libfdisk1-udeb"},
          {"reference": "libmount-dev"},
          {"reference": "libmount1"},
          {"reference": "libmount1-udeb"},
          {"reference": "libsmartcols-dev"},
          {"reference": "libsmartcols1"},
          {"reference": "libsmartcols1-udeb"},
          {"reference": "libuuid1"},
          {"reference": "libuuid1-udeb"},
          {"reference": "mount"},
          {"reference": "rfkill"},
          {"reference": "util-linux"},
          {"reference": "util-linux-extra"},
          {"reference": "util-linux-locales"},
          {"reference": "util-linux-udeb"},
          {"reference": "uuid-dev"},
          {"reference": "uuid-runtime"}
        ]
      }
    ]
  },
  "Debian Linux-13": {
    "package_manager": "dpkg-l",
    "constraints": [
      {
        "release": "13",
        "pkgs": [
          {"reference": "bsdextrautils"},
          {"reference": "bsdutils"},
          {"reference": "eject"},
          {"reference": "eject-udeb"},
          {"reference": "fdisk"},
          {"reference": "fdisk-udeb"},
          {"reference": "lastlog2"},
          {"reference": "libblkid-dev"},
          {"reference": "libblkid1"},
          {"reference": "libblkid1-udeb"},
          {"reference": "libfdisk-dev"},
          {"reference": "libfdisk1"},
          {"reference": "libfdisk1-udeb"},
          {"reference": "liblastlog2-2"},
          {"reference": "liblastlog2-dev"},
          {"reference": "libmount-dev"},
          {"reference": "libmount1"},
          {"reference": "libmount1-udeb"},
          {"reference": "libpam-lastlog2"},
          {"reference": "libsmartcols-dev"},
          {"reference": "libsmartcols1"},
          {"reference": "libsmartcols1-udeb"},
          {"reference": "libuuid1"},
          {"reference": "libuuid1-udeb"},
          {"reference": "login"},
          {"reference": "mount"},
          {"reference": "rfkill"},
          {"reference": "util-linux"},
          {"reference": "util-linux-extra"},
          {"reference": "util-linux-locales"},
          {"reference": "util-linux-udeb"},
          {"reference": "uuid-dev"},
          {"reference": "uuid-runtime"}
        ]
      }
    ]
  },
  "Debian Linux-14": {
    "package_manager": "dpkg-l",
    "constraints": [
      {
        "release": "14",
        "pkgs": [
          {"reference": "bsdextrautils"},
          {"reference": "bsdutils"},
          {"reference": "eject"},
          {"reference": "eject-udeb"},
          {"reference": "fdisk"},
          {"reference": "fdisk-udeb"},
          {"reference": "lastlog2"},
          {"reference": "libblkid-dev"},
          {"reference": "libblkid1"},
          {"reference": "libblkid1-udeb"},
          {"reference": "libfdisk-dev"},
          {"reference": "libfdisk1"},
          {"reference": "libfdisk1-udeb"},
          {"reference": "liblastlog2-2"},
          {"reference": "liblastlog2-dev"},
          {"reference": "libmount-dev"},
          {"reference": "libmount1"},
          {"reference": "libmount1-udeb"},
          {"reference": "libpam-lastlog2"},
          {"reference": "libsmartcols-dev"},
          {"reference": "libsmartcols1"},
          {"reference": "libsmartcols1-udeb"},
          {"reference": "libuuid1"},
          {"reference": "libuuid1-udeb"},
          {"reference": "login"},
          {"reference": "mount"},
          {"reference": "rfkill"},
          {"reference": "util-linux"},
          {"reference": "util-linux-extra"},
          {"reference": "util-linux-locales"},
          {"reference": "util-linux-udeb"},
          {"reference": "uuid-dev"},
          {"reference": "uuid-runtime"}
        ]
      }
    ]
  }
};

var distro_constraints_values = linux_unpatched::get_distro_constraints(distro_constraints_arr:distro_constraints_array);
if (empty_or_null(distro_constraints_values)) audit(AUDIT_HOST_NOT, 'affected');

var third_party_support = get_kb_item('Host/OS/extended-third-party');
if (!empty_or_null(third_party_support)) {
    var third_party_vendors = distro_constraints_values['third_party'];
    if (!empty_or_null(third_party_vendors)) {
        var vendor;
        foreach vendor (third_party_vendors) {
            if (vendor == third_party_support) exit(0, 'A third party management patch is available for this vulnerability from ' + vendor + '.\n');
        }
    }
}

var report = linux_unpatched::check_unpatched_constraints(distro_constraints_values:distro_constraints_values);

if (!empty_or_null(report))
{
  security_report_v4(
      port       : 0,
      severity   : SECURITY_NOTE,
      extra      : report
  );
  exit(0);
}
else
{
  audit(AUDIT_HOST_NOT, 'affected');
}