Linux Distros Unpatched Vulnerability : CVE-2026-71892

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

include('compat.inc');

if (description)
{
  script_id(362877);
  script_version("1.1");
  script_set_attribute(attribute:"plugin_modification_date", value:"2026/10/03");

  script_cve_id("CVE-2026-71892");

  script_name(english:"Linux Distros Unpatched Vulnerability : CVE-2026-71892");

  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.

  - In Bouncy Castle for Java before 1.86, the opt-in key-size validation on CMS key-transport recipients,
    org.bouncycastle.cms.jcajce.JceKeyTransRecipient.setKeySizeValidation(true), never ran for a message using
    RFC 9709 content-encryption key derivation (id-alg-cek-hkdf-sha256). The branch that should have selected
    the actual content-encryption algorithm carried in the key derivation AlgorithmIdentifier's parameters
    compared the encrypted-key byte array against the id-alg-cek-hkdf-sha256 object identifier, a comparison
    between a byte array and an ASN1ObjectIdentifier that is false for every possible input, so the check fell
    through to a key-size lookup on the outer wrapper OID. That OID identifies a key-derivation construction
    rather than a cipher and has no registered key size, so the size comparison was skipped entirely. A key-
    transport EnvelopedData or AuthEnvelopedData whose transported, HKDF-derived content-encryption key did
    not match the key size of the advertised content-encryption algorithm was therefore accepted even with
    validation explicitly enabled, silently defeating the only mechanism the API offers for enforcing
    recovered key size. The recipient now dispatches on the content-encryption AlgorithmIdentifier's algorithm
    OID, so validation checks the recovered key against the inner content-encryption algorithm. Messages with
    a matching key size, non-HKDF messages, and recipients that do not enable validation are unaffected. This
    issue also affects Bouncy Castle for Java FIPS (BC-FJA) before bcpkix-fips 2.0.13 (2.0.X series) and
    2.1.13 (2.1.X series). (CVE-2026-71892)

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-2026-71892");
  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:P/I:P/A:P");
  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:N/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N");
  script_set_attribute(attribute:"cvss4_supplemental", value:"CVSS:4.0/U:Amber");
  script_set_attribute(attribute:"cvss4_threat_vector", value:"CVSS:4.0/E:U");
  script_set_attribute(attribute:"cvss_score_source", value:"CVE-2026-71892");

  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:"2026/10/03");
  script_set_attribute(attribute:"plugin_publication_date", value:"2026/10/03");

  script_set_attribute(attribute:"plugin_type", value:"local");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:debian:debian_linux:12.0");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:debian:debian_linux:13.0");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:debian:debian_linux:bouncycastle");
  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-12", "Host/OS/Debian Linux-13");

  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-12": {
    "package_manager": "dpkg-l",
    "constraints": [
      {
        "release": "12",
        "pkgs": [
          {"reference": "libbcjmail-java"},
          {"reference": "libbcmail-java"},
          {"reference": "libbcpg-java"},
          {"reference": "libbcpkix-java"},
          {"reference": "libbcprov-java"},
          {"reference": "libbctls-java"},
          {"reference": "libbcutil-java"}
        ]
      }
    ]
  },
  "Debian Linux-13": {
    "package_manager": "dpkg-l",
    "constraints": [
      {
        "release": "13",
        "pkgs": [
          {"reference": "libbcjmail-java"},
          {"reference": "libbcmail-java"},
          {"reference": "libbcpg-java"},
          {"reference": "libbcpkix-java"},
          {"reference": "libbcprov-java"},
          {"reference": "libbctls-java"},
          {"reference": "libbcutil-java"}
        ]
      }
    ]
  }
};

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