Linux Distros Unpatched Vulnerability : CVE-2026-110985

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

include('compat.inc');

if (description)
{
  script_id(373856);
  script_version("1.1");
  script_set_attribute(attribute:"plugin_modification_date", value:"2026/10/29");

  script_cve_id("CVE-2026-110985");

  script_name(english:"Linux Distros Unpatched Vulnerability : CVE-2026-110985");

  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.

  - A Kafka broker using SASL/OAUTHBEARER with the default validator
    (sasl.oauthbearer.jwt.validator.class=DefaultJwtValidator) selects its implementation from configuration.
    When sasl.oauthbearer.jwks.endpoint.url is set, the validator verifies the JWT signature. When that URL is
    unset (the default) and no verification key resolver is supplied, DefaultJwtValidator silently falls back
    to ClientJwtValidator, which does not verify the JWT signature, algorithm, or issuer - and the broker
    starts with no warning or error. This is the residual of CVE-2026-33557, whose fix restored signature
    verification only on the path where the JWKS endpoint URL is set. Impact: A broker in this state accepts
    any structurally valid JWT, including alg:none tokens. An unauthenticated remote attacker who can
    reach the listener can forge a token asserting any principal - including configured superusers - and gain
    full access to the cluster. Only brokers that enable SASL/OAUTHBEARER validation without a JWKS endpoint
    URL (and without a custom verification key resolver) are affected; brokers that set the URL verify
    signatures and are not affected. Unlike CVE-2026-110952 (issuer/audience not enforced by default), here no
    signature is verified at all. Mitigation (all affected versions, no upgrade required): Set
    sasl.oauthbearer.jwks.endpoint.url for every listener/mechanism that uses
    OAuthBearerValidatorCallbackHandler, or configure a signature-verifying
    sasl.oauthbearer.jwt.validator.class. Resolution: From Apache Kafka 4.2.2, 4.3.1, and 4.4.0: a broker that
    would fall back to the non-verifying ClientJwtValidator fails to start with a ConfigException instead of
    running without signature verification (secure by default). (CVE-2026-110985)

Note that Nessus relies on the presence of the package as reported by the vendor.");
  script_set_attribute(attribute:"see_also", value:"https://ubuntu.com/security/CVE-2026-110985");
  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:P/A:N");
  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:N");
  script_set_cvss3_temporal_vector("CVSS:3.0/E:U/RL:U/RC:C");
  script_set_attribute(attribute:"cvss_score_source", value:"CVE-2026-110985");

  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:"2026/10/28");
  script_set_attribute(attribute:"plugin_publication_date", value:"2026/10/29");

  script_set_attribute(attribute:"plugin_type", value:"local");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:canonical:ubuntu_linux:18.04:-:lts");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:kafka");
  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/Ubuntu Linux-18.04");

  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 = {
  "Ubuntu Linux-18.04": {
    "package_manager": "dpkg-l",
    "constraints": [
      {
        "release": "18.04",
        "pkgs": [
          {"reference": "kafka"}
        ]
      }
    ]
  }
};

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');
}