Linux Distros Unpatched Vulnerability : CVE-2021-42521

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

include('compat.inc');

if (description)
{
  script_id(224178);
  script_version("1.7");
  script_set_attribute(attribute:"plugin_modification_date", value:"2026/04/13");

  script_cve_id("CVE-2021-42521");

  script_name(english:"Linux Distros Unpatched Vulnerability : CVE-2021-42521");

  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.

  - There is a NULL pointer dereference vulnerability in VTK before 9.2.5, and it lies in
    IO/Infovis/vtkXMLTreeReader.cxx. The vendor didn't check the return value of libxml2 API
    'xmlDocGetRootElement', and try to dereference it. It is unsafe as the return value can be NULL and that
    NULL pointer dereference may crash the application. (CVE-2021-42521)

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-2021-42521");
  script_set_attribute(attribute:"see_also", value:"https://ubuntu.com/security/CVE-2021-42521");
  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:N/I:N/A:P");
  script_set_cvss_temporal_vector("CVSS2#E:POC/RL:U/RC:C");
  script_set_cvss3_base_vector("CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H");
  script_set_cvss3_temporal_vector("CVSS:3.0/E:P/RL:U/RC:C");
  script_set_attribute(attribute:"cvss_score_source", value:"CVE-2021-42521");

  script_set_attribute(attribute:"exploitability_ease", value:"Exploits are available");
  script_set_attribute(attribute:"exploit_available", value:"true");
  script_set_attribute(attribute:"vendor_unpatched", value:"true");

  script_set_attribute(attribute:"vuln_publication_date", value:"2022/08/25");
  script_set_attribute(attribute:"plugin_publication_date", value:"2025/03/05");

  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:25.04");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:debian:debian_linux:11.0");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:debian:debian_linux:12.0");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:vtk");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:vtk6");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:vtk7");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:vtk9");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:debian:debian_linux:vtk6");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:debian:debian_linux:vtk7");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:debian:debian_linux:vtk9");
  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) 2025-2026 and is owned by Tenable, Inc. or an Affiliate thereof.");

  script_dependencies("set_linux_os_id.nasl", "ssh_get_info2.nasl");
  script_require_keys("Host/OS/identifier", "Host/cpu", "Host/local_checks_enabled", "global_settings/vendor_unpatched");
  script_require_ports("Host/OS/Debian Linux-11", "Host/OS/Debian Linux-12", "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-25.04");

  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-11": {
    "package_manager": "dpkg-l",
    "constraints": [
      {
        "release": "11",
        "pkgs": [
          {"reference": "libvtk6-dev"},
          {"reference": "libvtk6-qt-dev"},
          {"reference": "libvtk6.3"},
          {"reference": "libvtk6.3-qt"},
          {"reference": "libvtk7-dev"},
          {"reference": "libvtk7-java"},
          {"reference": "libvtk7-jni"},
          {"reference": "libvtk7-qt-dev"},
          {"reference": "libvtk7.1p"},
          {"reference": "libvtk7.1p-qt"},
          {"reference": "libvtk9"},
          {"reference": "libvtk9-dev"},
          {"reference": "libvtk9-java"},
          {"reference": "libvtk9-qt"},
          {"reference": "libvtk9-qt-dev"},
          {"reference": "python3-vtk7"},
          {"reference": "python3-vtk9"},
          {"reference": "tcl-vtk7"},
          {"reference": "vtk7"},
          {"reference": "vtk7-doc"},
          {"reference": "vtk7-examples"},
          {"reference": "vtk9"},
          {"reference": "vtk9-doc"},
          {"reference": "vtk9-examples"}
        ]
      }
    ]
  },
  "Debian Linux-12": {
    "package_manager": "dpkg-l",
    "constraints": [
      {
        "release": "12",
        "pkgs": [
          {"reference": "libvtk9-dev"},
          {"reference": "libvtk9-java"},
          {"reference": "libvtk9-qt-dev"},
          {"reference": "libvtk9.1"},
          {"reference": "libvtk9.1-qt"},
          {"reference": "python3-vtk9"},
          {"reference": "vtk9"},
          {"reference": "vtk9-doc"},
          {"reference": "vtk9-examples"}
        ]
      }
    ]
  },
  "Ubuntu Linux-14.04": {
    "package_manager": "dpkg-l",
    "constraints": [
      {
        "release": "14.04",
        "pkgs": [
          {"reference": "vtk"},
          {"reference": "vtk6"}
        ]
      }
    ]
  },
  "Ubuntu Linux-16.04": {
    "package_manager": "dpkg-l",
    "constraints": [
      {
        "release": "16.04",
        "pkgs": [
          {"reference": "vtk"},
          {"reference": "vtk6"}
        ]
      }
    ]
  },
  "Ubuntu Linux-18.04": {
    "package_manager": "dpkg-l",
    "constraints": [
      {
        "release": "18.04",
        "pkgs": [
          {"reference": "vtk6"},
          {"reference": "vtk7"}
        ]
      }
    ]
  },
  "Ubuntu Linux-20.04": {
    "package_manager": "dpkg-l",
    "constraints": [
      {
        "release": "20.04",
        "pkgs": [
          {"reference": "vtk6"},
          {"reference": "vtk7"}
        ]
      }
    ]
  },
  "Ubuntu Linux-22.04": {
    "package_manager": "dpkg-l",
    "constraints": [
      {
        "release": "22.04",
        "pkgs": [
          {"reference": "vtk7"},
          {"reference": "vtk9"}
        ]
      }
    ]
  },
  "Ubuntu Linux-24.04": {
    "package_manager": "dpkg-l",
    "constraints": [
      {
        "release": "24.04",
        "pkgs": [
          {"reference": "vtk9"}
        ]
      }
    ]
  },
  "Ubuntu Linux-25.04": {
    "package_manager": "dpkg-l",
    "constraints": [
      {
        "release": "25.04",
        "pkgs": [
          {"reference": "vtk9"}
        ]
      }
    ]
  }
};

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

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