Linux Distros Unpatched Vulnerability : CVE-2021-28688

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

include('compat.inc');

if (description)
{
  script_id(253757);
  script_version("1.8");
  script_set_attribute(attribute:"plugin_modification_date", value:"2026/05/21");

  script_cve_id("CVE-2021-28688");

  script_name(english:"Linux Distros Unpatched Vulnerability : CVE-2021-28688");

  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 fix for XSA-365 includes initialization of pointers such that subsequent cleanup code wouldn't use
    uninitialized or stale values. This initialization went too far and may under certain conditions also
    overwrite pointers which are in need of cleaning up. The lack of cleanup would result in leaking
    persistent grants. The leak in turn would prevent fully cleaning up after a respective guest has died,
    leaving around zombie domains. All Linux versions having the fix for XSA-365 applied are vulnerable.
    XSA-365 was classified to affect versions back to at least 3.11. (CVE-2021-28688)

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-2021-28688");
  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:L/AC:L/Au:N/C:N/I:N/A:P");
  script_set_cvss_temporal_vector("CVSS2#E:U/RL:U/RC:C");
  script_set_cvss3_base_vector("CVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:C/C:N/I:N/A:H");
  script_set_cvss3_temporal_vector("CVSS:3.0/E:U/RL:U/RC:C");
  script_set_attribute(attribute:"cvss_score_source", value:"CVE-2021-28688");

  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:"2021/04/06");
  script_set_attribute(attribute:"plugin_publication_date", value:"2025/08/24");

  script_set_attribute(attribute:"plugin_type", value:"local");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:canonical:ubuntu_linux:14.04:-:lts");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:canonical:ubuntu_linux:16.04:-:lts");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:canonical:ubuntu_linux:18.04:-:lts");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:canonical:ubuntu_linux:20.04:-:lts");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:canonical:ubuntu_linux:22.04:-:lts");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:canonical:ubuntu_linux:24.04:-:lts");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:linux");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:linux-aws-5.0");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:linux-aws-5.3");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:linux-azure");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:linux-azure-5.3");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:linux-azure-edge");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:linux-azure-fde-5.15");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:linux-gcp");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:linux-gcp-5.3");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:linux-gcp-edge");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:linux-gke-4.15");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:linux-hwe");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:linux-hwe-edge");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:linux-intel-iot-realtime");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:linux-oem");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:linux-oem-5.6");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:linux-oracle-5.0");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:linux-oracle-5.3");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:linux-raspi-realtime");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:linux-raspi2");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:linux-realtime");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:linux-riscv");
  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) 2025-2026 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-14.04", "Host/OS/Ubuntu Linux-16.04", "Host/OS/Ubuntu Linux-18.04", "Host/OS/Ubuntu Linux-20.04", "Host/OS/Ubuntu Linux-22.04", "Host/OS/Ubuntu Linux-24.04");

  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-14.04": {
    "package_manager": "dpkg-l",
    "constraints": [
      {
        "release": "14.04",
        "pkgs": [
          {"reference": "linux-cloud-tools-3.13.0"},
          {"reference": "linux-cloud-tools-common"},
          {"reference": "linux-doc"},
          {"reference": "linux-headers-3.13.0"},
          {"reference": "linux-image-3.13.0"},
          {"reference": "linux-image-extra-3.13.0"},
          {"reference": "linux-libc-dev"},
          {"reference": "linux-source-3.13.0"},
          {"reference": "linux-tools-3.13.0"},
          {"reference": "linux-tools-common"},
          {"reference": "linux-udebs-generic"},
          {"reference": "linux-udebs-generic-lpae"},
          {"reference": "linux-udebs-lowlatency"}
        ]
      }
    ]
  },
  "Ubuntu Linux-16.04": {
    "package_manager": "dpkg-l",
    "constraints": [
      {
        "release": "16.04",
        "pkgs": [
          {"reference": "linux-hwe-edge"}
        ]
      }
    ]
  },
  "Ubuntu Linux-18.04": {
    "package_manager": "dpkg-l",
    "constraints": [
      {
        "release": "18.04",
        "pkgs": [
          {"reference": "linux-aws-5.0"},
          {"reference": "linux-aws-5.3"},
          {"reference": "linux-azure-5.3"},
          {"reference": "linux-azure-cloud-tools-4.15.0"},
          {"reference": "linux-azure-edge"},
          {"reference": "linux-azure-headers-4.15.0"},
          {"reference": "linux-azure-tools-4.15.0"},
          {"reference": "linux-cloud-tools-4.15.0"},
          {"reference": "linux-gcp-5.3"},
          {"reference": "linux-gcp-edge"},
          {"reference": "linux-gcp-headers-4.15.0"},
          {"reference": "linux-gcp-tools-4.15.0"},
          {"reference": "linux-gke-4.15"},
          {"reference": "linux-headers-4.15.0"},
          {"reference": "linux-hwe"},
          {"reference": "linux-hwe-edge"},
          {"reference": "linux-image-4.15.0"},
          {"reference": "linux-image-unsigned-4.15.0"},
          {"reference": "linux-modules-4.15.0"},
          {"reference": "linux-modules-extra-4.15.0"},
          {"reference": "linux-oem-headers-4.15.0"},
          {"reference": "linux-oem-tools-4.15.0"},
          {"reference": "linux-oracle-5.0"},
          {"reference": "linux-oracle-5.3"},
          {"reference": "linux-tools-4.15.0"},
          {"reference": "linux-udebs-azure"},
          {"reference": "linux-udebs-oem"}
        ]
      }
    ]
  },
  "Ubuntu Linux-20.04": {
    "package_manager": "dpkg-l",
    "constraints": [
      {
        "release": "20.04",
        "pkgs": [
          {"reference": "linux-azure-fde-5.15"},
          {"reference": "linux-buildinfo-5.4.0"},
          {"reference": "linux-buildinfo-5.6.0"},
          {"reference": "linux-cloud-tools-5.4.0"},
          {"reference": "linux-cloud-tools-5.6.0"},
          {"reference": "linux-headers-5.4.0"},
          {"reference": "linux-headers-5.6.0"},
          {"reference": "linux-image-5.4.0"},
          {"reference": "linux-image-unsigned-5.6.0"},
          {"reference": "linux-libc-dev"},
          {"reference": "linux-modules-5.4.0"},
          {"reference": "linux-modules-5.6.0"},
          {"reference": "linux-modules-extra-5.4.0"},
          {"reference": "linux-modules-extra-5.6.0"},
          {"reference": "linux-oem-5.6-headers-5.6.0"},
          {"reference": "linux-oem-5.6-tools-5.6.0"},
          {"reference": "linux-oem-5.6-tools-common"},
          {"reference": "linux-oem-5.6-tools-host"},
          {"reference": "linux-raspi2"},
          {"reference": "linux-riscv-headers-5.4.0"},
          {"reference": "linux-riscv-tools-5.4.0"},
          {"reference": "linux-tools-5.4.0"},
          {"reference": "linux-tools-5.6.0"},
          {"reference": "linux-udebs-generic"},
          {"reference": "linux-udebs-oem"}
        ]
      }
    ]
  },
  "Ubuntu Linux-22.04": {
    "package_manager": "dpkg-l",
    "constraints": [
      {
        "release": "22.04",
        "pkgs": [
          {"reference": "linux-intel-iot-realtime"},
          {"reference": "linux-realtime"}
        ]
      }
    ]
  },
  "Ubuntu Linux-24.04": {
    "package_manager": "dpkg-l",
    "constraints": [
      {
        "release": "24.04",
        "pkgs": [
          {"reference": "linux-raspi-realtime"}
        ]
      }
    ]
  }
};

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