Linux Distros Unpatched Vulnerability : CVE-2021-23841

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

include('compat.inc');

if (description)
{
  script_id(223650);
  script_version("1.3");
  script_set_attribute(attribute:"plugin_modification_date", value:"2025/08/20");

  script_cve_id("CVE-2021-23841");
  script_xref(name:"CEA-ID", value:"CEA-2021-0025");

  script_name(english:"Linux Distros Unpatched Vulnerability : CVE-2021-23841");

  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 OpenSSL public API function X509_issuer_and_serial_hash() attempts to create a unique hash value based
    on the issuer and serial number data contained within an X509 certificate. However it fails to correctly
    handle any errors that may occur while parsing the issuer field (which might occur if the issuer field is
    maliciously constructed). This may subsequently result in a NULL pointer deref and a crash leading to a
    potential denial of service attack. The function X509_issuer_and_serial_hash() is never directly called by
    OpenSSL itself so applications are only vulnerable if they use this function directly and they use it on
    certificates that may have been obtained from untrusted sources. OpenSSL versions 1.1.1i and below are
    affected by this issue. Users of these versions should upgrade to OpenSSL 1.1.1j. OpenSSL versions 1.0.2x
    and below are affected by this issue. However OpenSSL 1.0.2 is out of support and no longer receiving
    public updates. Premium support customers of OpenSSL 1.0.2 should upgrade to 1.0.2y. Other users should
    upgrade to 1.1.1j. Fixed in OpenSSL 1.1.1j (Affected 1.1.1-1.1.1i). Fixed in OpenSSL 1.0.2y (Affected
    1.0.2-1.0.2x). (CVE-2021-23841)

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-2021-23841");
  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:N/I:N/A:P");
  script_set_cvss_temporal_vector("CVSS2#E:U/RL:OF/RC:C");
  script_set_cvss3_base_vector("CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H");
  script_set_cvss3_temporal_vector("CVSS:3.0/E:U/RL:O/RC:C");
  script_set_attribute(attribute:"cvss_score_source", value:"CVE-2021-23841");

  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:"2021/02/16");
  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:7");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:centos:centos:8");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:redhat:enterprise_linux:7");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:redhat:enterprise_linux:8");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:centos:centos:AAVMF");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:centos:centos:OVMF");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:centos:centos:compat-openssl10");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:centos:centos:openssl098e");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:centos:centos:ovmf");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:redhat:enterprise_linux:AAVMF");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:redhat:enterprise_linux:OVMF");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:redhat:enterprise_linux:compat-openssl10");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:redhat:enterprise_linux:openssl098e");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:redhat:enterprise_linux:ovmf");
  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-7", "Host/OS/CentOS Linux-8", "Host/OS/Red Hat Enterprise Linux-7", "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-7": {
    "package_manager": "rpm-list",
    "constraints": [
      {
        "release": "7",
        "pkgs": [
          {"reference": "AAVMF"},
          {"reference": "OVMF"},
          {"reference": "openssl098e"},
          {"reference": "ovmf"}
        ]
      }
    ]
  },
  "Red Hat Enterprise Linux-7": {
    "package_manager": "rpm-list",
    "constraints": [
      {
        "release": "7",
        "pkgs": [
          {"reference": "AAVMF"},
          {"reference": "OVMF"},
          {"reference": "openssl098e"},
          {"reference": "ovmf"}
        ]
      }
    ]
  },
  "CentOS Linux-8": {
    "package_manager": "rpm-list",
    "constraints": [
      {
        "release": "8",
        "pkgs": [
          {"reference": "compat-openssl10"}
        ]
      }
    ]
  },
  "Red Hat Enterprise Linux-8": {
    "package_manager": "rpm-list",
    "constraints": [
      {
        "release": "8",
        "pkgs": [
          {"reference": "compat-openssl10"}
        ]
      }
    ]
  }
};

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');
}