Linux Distros Unpatched Vulnerability : CVE-2018-20839

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

include('compat.inc');

if (description)
{
  script_id(222127);
  script_version("1.3");
  script_set_attribute(attribute:"plugin_modification_date", value:"2025/09/03");

  script_cve_id("CVE-2018-20839");

  script_name(english:"Linux Distros Unpatched Vulnerability : CVE-2018-20839");

  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.

  - systemd 242 changes the VT1 mode upon a logout, which allows attackers to read cleartext passwords in
    certain circumstances, such as watching a shutdown, or using Ctrl-Alt-F1 and Ctrl-Alt-F2. This occurs
    because the KDGKBMODE (aka current keyboard mode) check is mishandled. (CVE-2018-20839)

Note that Nessus relies on the presence of the package as reported by the vendor.");
  script_set_attribute(attribute:"see_also", value:"https://access.redhat.com/security/cve/cve-2018-20839");
  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:M/Au:N/C:P/I:N/A:N");
  script_set_cvss_temporal_vector("CVSS2#E:U/RL:OF/RC:C");
  script_set_cvss3_base_vector("CVSS:3.0/AV:P/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N");
  script_set_cvss3_temporal_vector("CVSS:3.0/E:U/RL:O/RC:C");
  script_set_attribute(attribute:"cvss_score_source", value:"CVE-2018-20839");

  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:"2019/05/17");
  script_set_attribute(attribute:"plugin_publication_date", value:"2025/03/04");

  script_set_attribute(attribute:"plugin_type", value:"local");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:centos:centos:8");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:redhat:enterprise_linux:8");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:centos:centos:systemd");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:centos:centos:systemd-container");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:centos:centos:systemd-devel");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:centos:centos:systemd-journal-remote");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:centos:centos:systemd-libs");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:centos:centos:systemd-pam");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:centos:centos:systemd-tests");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:centos:centos:systemd-udev");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:redhat:enterprise_linux:systemd");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:redhat:enterprise_linux:systemd-container");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:redhat:enterprise_linux:systemd-devel");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:redhat:enterprise_linux:systemd-journal-remote");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:redhat:enterprise_linux:systemd-libs");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:redhat:enterprise_linux:systemd-pam");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:redhat:enterprise_linux:systemd-tests");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:redhat:enterprise_linux:systemd-udev");
  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 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/CentOS Linux-8", "Host/OS/Red Hat Enterprise Linux-8");

  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/CentOS/rpm-list")) && empty_or_null(get_one_kb_item("Host/RedHat/rpm-list"))) audit(AUDIT_PACKAGE_LIST_MISSING);

include('linux_unpatched.inc');

var distro_constraints_array = {
  "CentOS Linux-8": {
    "package_manager": "rpm-list",
    "constraints": [
      {
        "release": "8",
        "pkgs": [
          {"reference": "systemd"},
          {"reference": "systemd-container"},
          {"reference": "systemd-devel"},
          {"reference": "systemd-journal-remote"},
          {"reference": "systemd-libs"},
          {"reference": "systemd-pam"},
          {"reference": "systemd-tests"},
          {"reference": "systemd-udev"}
        ]
      }
    ]
  },
  "Red Hat Enterprise Linux-8": {
    "package_manager": "rpm-list",
    "constraints": [
      {
        "release": "8",
        "pkgs": [
          {"reference": "systemd"},
          {"reference": "systemd-container"},
          {"reference": "systemd-devel"},
          {"reference": "systemd-journal-remote"},
          {"reference": "systemd-libs"},
          {"reference": "systemd-pam"},
          {"reference": "systemd-tests"},
          {"reference": "systemd-udev"}
        ]
      }
    ]
  }
};

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');
}