Linux Distros Unpatched Vulnerability : CVE-2026-109518

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

include('compat.inc');

if (description)
{
  script_id(376186);
  script_version("1.2");
  script_set_attribute(attribute:"plugin_modification_date", value:"2026/11/05");

  script_cve_id("CVE-2026-109518");

  script_name(english:"Linux Distros Unpatched Vulnerability : CVE-2026-109518");

  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.

  - On Debian, Ubuntu, and derivative Linux distributions, an on-path attacker who can manipulate the HTTP
    traffic (including a malicious mirror or proxy) between an APT client and an archive server triggered by a
    package install can trick the client into installing an attacker-controlled unverified package and achieve
    remote code execution with root privileges. The vulnerability is caused by the reuse of hard links and
    requires the client to follow redirects and retry the download of package files. It requires the client to
    have a non-zero Acquire::Retries configuration setting; the value 3 is the default starting with Debian 12
    (bookworm) and Ubuntu 22.04 LTS (Jammy Jellyfish), so older releases are unaffected in a default
    configuration (CVE-2026-109518)

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-2026-109518");
  script_set_attribute(attribute:"see_also", value:"https://ubuntu.com/security/CVE-2026-109518");
  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:N/AC:L/Au:N/C:C/I:C/A:C");
  script_set_cvss_temporal_vector("CVSS2#E:U/RL:U/RC:C");
  script_set_cvss3_base_vector("CVSS:3.0/AV:N/AC:L/PR:N/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:"cvss4_vector", value:"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N");
  script_set_attribute(attribute:"cvss4_threat_vector", value:"CVSS:4.0/E:U");
  script_set_attribute(attribute:"cvss_score_source", value:"CVE-2026-109518");

  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:"2026/11/04");
  script_set_attribute(attribute:"plugin_publication_date", value:"2026/11/04");

  script_set_attribute(attribute:"plugin_type", value:"local");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:canonical:ubuntu_linux:14.04:-:lts");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:canonical:ubuntu_linux:16.04:-:lts");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:canonical:ubuntu_linux:18.04:-:lts");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:canonical:ubuntu_linux:20.04:-:lts");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:canonical:ubuntu_linux:22.04:-:lts");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:canonical:ubuntu_linux:24.04:-:lts");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:canonical:ubuntu_linux:26.04:-:lts");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:canonical:ubuntu_linux:26.10");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:debian:debian_linux:14.0");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:apt");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:debian:debian_linux:apt");
  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-14", "Host/OS/Ubuntu Linux-14.04", "Host/OS/Ubuntu Linux-16.04", "Host/OS/Ubuntu Linux-18.04", "Host/OS/Ubuntu Linux-20.04", "Host/OS/Ubuntu Linux-22.04", "Host/OS/Ubuntu Linux-24.04", "Host/OS/Ubuntu Linux-26.04", "Host/OS/Ubuntu Linux-26.10");

  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-14": {
    "package_manager": "dpkg-l",
    "constraints": [
      {
        "release": "14",
        "pkgs": [
          {"reference": "apt"},
          {"reference": "apt-doc"},
          {"reference": "apt-transport-https"},
          {"reference": "apt-utils"},
          {"reference": "libapt-pkg-dev"},
          {"reference": "libapt-pkg-doc"},
          {"reference": "libapt-pkg7.0"}
        ]
      }
    ]
  },
  "Ubuntu Linux-26.04": {
    "package_manager": "dpkg-l",
    "constraints": [
      {
        "release": "26.04",
        "pkgs": [
          {"reference": "apt"},
          {"reference": "apt-doc"},
          {"reference": "apt-transport-https"},
          {"reference": "apt-utils"},
          {"reference": "libapt-pkg-dev"},
          {"reference": "libapt-pkg-doc"},
          {"reference": "libapt-pkg7.0"}
        ]
      }
    ]
  },
  "Ubuntu Linux-26.10": {
    "package_manager": "dpkg-l",
    "constraints": [
      {
        "release": "26.10",
        "pkgs": [
          {"reference": "apt"},
          {"reference": "apt-doc"},
          {"reference": "apt-transport-https"},
          {"reference": "apt-utils"},
          {"reference": "libapt-pkg-dev"},
          {"reference": "libapt-pkg-doc"},
          {"reference": "libapt-pkg7.0"}
        ]
      }
    ]
  },
  "Ubuntu Linux-14.04": {
    "package_manager": "dpkg-l",
    "constraints": [
      {
        "release": "14.04",
        "pkgs": [
          {"reference": "apt"},
          {"reference": "apt-doc"},
          {"reference": "apt-transport-https"},
          {"reference": "apt-utils"},
          {"reference": "libapt-inst1.5"},
          {"reference": "libapt-pkg-dev"},
          {"reference": "libapt-pkg-doc"},
          {"reference": "libapt-pkg4.12"}
        ]
      }
    ]
  },
  "Ubuntu Linux-16.04": {
    "package_manager": "dpkg-l",
    "constraints": [
      {
        "release": "16.04",
        "pkgs": [
          {"reference": "apt"},
          {"reference": "apt-doc"},
          {"reference": "apt-transport-https"},
          {"reference": "apt-utils"},
          {"reference": "libapt-inst2.0"},
          {"reference": "libapt-pkg-dev"},
          {"reference": "libapt-pkg-doc"},
          {"reference": "libapt-pkg5.0"}
        ]
      }
    ]
  },
  "Ubuntu Linux-18.04": {
    "package_manager": "dpkg-l",
    "constraints": [
      {
        "release": "18.04",
        "pkgs": [
          {"reference": "apt"},
          {"reference": "apt-doc"},
          {"reference": "apt-transport-https"},
          {"reference": "apt-utils"},
          {"reference": "libapt-inst2.0"},
          {"reference": "libapt-pkg-dev"},
          {"reference": "libapt-pkg-doc"},
          {"reference": "libapt-pkg5.0"}
        ]
      }
    ]
  },
  "Ubuntu Linux-20.04": {
    "package_manager": "dpkg-l",
    "constraints": [
      {
        "release": "20.04",
        "pkgs": [
          {"reference": "apt"},
          {"reference": "apt-doc"},
          {"reference": "apt-transport-https"},
          {"reference": "apt-utils"},
          {"reference": "libapt-pkg-dev"},
          {"reference": "libapt-pkg-doc"},
          {"reference": "libapt-pkg6.0"}
        ]
      }
    ]
  },
  "Ubuntu Linux-22.04": {
    "package_manager": "dpkg-l",
    "constraints": [
      {
        "release": "22.04",
        "pkgs": [
          {"reference": "apt"},
          {"reference": "apt-doc"},
          {"reference": "apt-transport-https"},
          {"reference": "apt-utils"},
          {"reference": "libapt-pkg-dev"},
          {"reference": "libapt-pkg-doc"},
          {"reference": "libapt-pkg6.0"}
        ]
      }
    ]
  },
  "Ubuntu Linux-24.04": {
    "package_manager": "dpkg-l",
    "constraints": [
      {
        "release": "24.04",
        "pkgs": [
          {"reference": "apt"},
          {"reference": "apt-doc"},
          {"reference": "apt-transport-https"},
          {"reference": "apt-utils"},
          {"reference": "libapt-pkg-dev"},
          {"reference": "libapt-pkg-doc"},
          {"reference": "libapt-pkg6.0t64"}
        ]
      }
    ]
  }
};

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_HOLE,
      extra      : report
  );
  exit(0);
}
else
{
  audit(AUDIT_HOST_NOT, 'affected');
}