Security Update for Microsoft .NET Core (February 2026)

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

include('compat.inc');

if (description)
{
  script_id(298547);
  script_version("1.4");
  script_set_attribute(attribute:"plugin_modification_date", value:"2026/05/19");

  script_cve_id("CVE-2026-21218");
  script_xref(name:"IAVA", value:"2026-A-0123-S");

  script_name(english:"Security Update for Microsoft .NET Core (February 2026)");

  script_set_attribute(attribute:"synopsis", value:
"The remote Windows host is affected by a .NET Core vulnerability");
  script_set_attribute(attribute:"description", value:
"The version of tested product installed on the remote host is prior to tested version. It is, therefore, affected by a
vulnerability as referenced in the vendor advisory.

  - .NET Spoofing Vulnerability (CVE-2026-21218)

Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version
number.");
  script_set_attribute(attribute:"see_also", value:"https://github.com/dotnet/core/issues/10250");
  # https://github.com/dotnet/core/blob/main/release-notes/8.0/8.0.24/8.0.24.md
  script_set_attribute(attribute:"see_also", value:"http://www.nessus.org/u?cd7bd73c");
  script_set_attribute(attribute:"see_also", value:"https://dotnet.microsoft.com/en-us/download/dotnet/8.0");
  script_set_attribute(attribute:"see_also", value:"https://support.microsoft.com/help/5077863");
  # https://github.com/dotnet/core/blob/master/release-notes/9.0/9.0.13/9.0.13.md
  script_set_attribute(attribute:"see_also", value:"http://www.nessus.org/u?a0a4aab4");
  script_set_attribute(attribute:"see_also", value:"https://dotnet.microsoft.com/download/dotnet/9.0");
  script_set_attribute(attribute:"see_also", value:"https://support.microsoft.com/help/5077864");
  # https://github.com/dotnet/core/blob/main/release-notes/10.0/10.0.3/10.0.3.md
  script_set_attribute(attribute:"see_also", value:"http://www.nessus.org/u?21a6680a");
  script_set_attribute(attribute:"see_also", value:"https://dotnet.microsoft.com/download/dotnet/10.0");
  script_set_attribute(attribute:"see_also", value:"https://support.microsoft.com/help/5077862");
  script_set_attribute(attribute:"see_also", value:"https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-21218");
  script_set_attribute(attribute:"solution", value:
"Update .NET Core, remove vulnerable packages and refer to vendor advisory.");
  script_set_cvss_base_vector("CVSS2#AV:N/AC:L/Au:N/C:N/I:C/A:N");
  script_set_cvss_temporal_vector("CVSS2#E:U/RL:OF/RC:C");
  script_set_cvss3_base_vector("CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/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-2026-21218");

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

  script_set_attribute(attribute:"vuln_publication_date", value:"2026/02/10");
  script_set_attribute(attribute:"patch_publication_date", value:"2026/02/10");
  script_set_attribute(attribute:"plugin_publication_date", value:"2026/02/10");

  script_set_attribute(attribute:"plugin_type", value:"local");
  script_set_attribute(attribute:"cpe", value:"cpe:/a:microsoft:.net_core");
  script_set_attribute(attribute:"stig_severity", value:"I");
  script_end_attributes();

  script_category(ACT_GATHER_INFO);
  script_family(english:"Windows");

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

  script_dependencies("microsoft_dotnet_core_win.nbin");
  script_require_keys("installed_sw/.NET Core Windows");

  exit(0);
}

include('vdf.inc');

# @tvdl-content
var vuln_data = {
  'metadata': {'spec_version': '1.0'},
  'requires': [
    {'scope': 'target', 'match': {'os': 'windows'}}
  ],
  'checks': [
    {
      'product': {'name': '.NET Core Windows', 'type': 'app'},
      'check_algorithm': 'default',
      'constraints': [
        { 'min_version' : '8.0.0', 'fixed_version' : '8.0.24' },
        { 'min_version' : '9.0.0', 'fixed_version' : '9.0.13' },
        { 'min_version' : '10.0.0', 'fixed_version' : '10.0.3' }
      ]
    }
  ]
};

var result = vdf::check_and_report(vuln_data:vuln_data, severity:SECURITY_HOLE);
vdf::handle_check_and_report_errors(vdf_result:result);