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Linux Distros Unpatched Vulnerability : CVE-2021-4095

🗓️ 05 Mar 2025 00:00:00Reported by TenableType 
nessus
 nessus🔗 www.tenable.com👁 5 Views

Linux hosts contain unpatched vulnerability CVE-2021-4095, allowing denial of service attacks.

Related
Refs
Code
ReporterTitlePublishedViews
Family
ATTACKERKB		CVE-2021-4095
10 Mar 202217:44
–attackerkb
BDU FSTEC		The vulnerability of the KVM virtualization subsystem in the Linux operating system allows a hacker to trigger a service failure.
14 Jun 202200:00
–bdu_fstec
CBLMariner		CVE-2021-4095 affecting package kernel 5.10.189.1-1
7 Apr 202206:04
–cbl_mariner
CBLMariner		CVE-2021-4095 affecting package kernel for versions less than 5.15.37.1-2
3 Jun 202217:54
–cbl_mariner
Circl		CVE-2021-4095
19 Mar 202600:00
–circl
CNNVD		Linux kernel 代码问题漏洞
14 Dec 202100:00
–cnnvd
CNVD		Linux Kernel kvm_dirty_ring_get() function denial of service vulnerability
24 Dec 202100:00
–cnvd
CVE		CVE-2021-4095
8 Mar 202214:05
–cve
Cvelist		CVE-2021-4095
8 Mar 202214:05
–cvelist
Debian CVE		CVE-2021-4095
8 Mar 202214:05
–debiancve
Rows per page
#%NASL_MIN_LEVEL 80900
##
# (C) Tenable, Inc.
##

include('compat.inc');

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  script_version("1.11");
  script_set_attribute(attribute:"plugin_modification_date", value:"2026/05/21");

  script_cve_id("CVE-2021-4095");

  script_name(english:"Linux Distros Unpatched Vulnerability : CVE-2021-4095");

  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 NULL pointer dereference was found in the Linux kernel's KVM when dirty ring logging is enabled without
    an active vCPU context. An unprivileged local attacker on the host may use this flaw to cause a kernel
    oops condition and thus a denial of service by issuing a KVM_XEN_HVM_SET_ATTR ioctl. This flaw affects
    Linux kernel versions prior to 5.17-rc1. (CVE-2021-4095)

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-2021-4095");
  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:M/Au:N/C:N/I:N/A:P");
  script_set_cvss_temporal_vector("CVSS2#E:POC/RL:U/RC:C");
  script_set_cvss3_base_vector("CVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H");
  script_set_cvss3_temporal_vector("CVSS:3.0/E:P/RL:U/RC:C");
  script_set_attribute(attribute:"cvss_score_source", value:"CVE-2021-4095");

  script_set_attribute(attribute:"exploitability_ease", value:"Exploits are available");
  script_set_attribute(attribute:"exploit_available", value:"true");
  script_set_attribute(attribute:"vendor_unpatched", value:"true");

  script_set_attribute(attribute:"vuln_publication_date", value:"2022/03/08");
  script_set_attribute(attribute:"plugin_publication_date", value:"2025/03/05");

  script_set_attribute(attribute:"plugin_type", value:"local");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:canonical:ubuntu_linux:16.04:-:lts");
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  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");
  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-5.13");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:linux-aws-5.15");
  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-aws-5.8");
  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-5.13");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:linux-azure-5.15");
  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-5.8");
  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");
  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-5.13");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:linux-gcp-5.15");
  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-5.8");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:linux-gke");
  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-gke-5.15");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:linux-gkeop");
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  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:linux-oem");
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  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("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/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-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-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-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-aws-5.13"},
          {"reference": "linux-aws-5.15"},
          {"reference": "linux-aws-5.8"},
          {"reference": "linux-azure-5.13"},
          {"reference": "linux-azure-5.15"},
          {"reference": "linux-azure-5.8"},
          {"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-gcp-5.13"},
          {"reference": "linux-gcp-5.15"},
          {"reference": "linux-gcp-5.8"},
          {"reference": "linux-gke-5.15"},
          {"reference": "linux-gkeop-5.15"},
          {"reference": "linux-headers-5.4.0"},
          {"reference": "linux-headers-5.6.0"},
          {"reference": "linux-hwe-5.11"},
          {"reference": "linux-hwe-5.13"},
          {"reference": "linux-hwe-5.15"},
          {"reference": "linux-hwe-5.8"},
          {"reference": "linux-ibm-5.15"},
          {"reference": "linux-image-5.4.0"},
          {"reference": "linux-image-unsigned-5.6.0"},
          {"reference": "linux-intel-5.13"},
          {"reference": "linux-intel-iotg-5.15"},
          {"reference": "linux-libc-dev"},
          {"reference": "linux-lowlatency-hwe-5.15"},
          {"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-nvidia-tegra-5.15"},
          {"reference": "linux-oem-5.13"},
          {"reference": "linux-oem-5.14"},
          {"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-oracle-5.13"},
          {"reference": "linux-oracle-5.15"},
          {"reference": "linux-oracle-5.8"},
          {"reference": "linux-raspi2"},
          {"reference": "linux-riscv-5.15"},
          {"reference": "linux-riscv-5.8"},
          {"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-aws-cloud-tools-5.15.0"},
          {"reference": "linux-aws-headers-5.15.0"},
          {"reference": "linux-aws-tools-5.15.0"},
          {"reference": "linux-azure-cloud-tools-5.15.0"},
          {"reference": "linux-azure-fde"},
          {"reference": "linux-azure-headers-5.15.0"},
          {"reference": "linux-azure-tools-5.15.0"},
          {"reference": "linux-buildinfo-5.15.0"},
          {"reference": "linux-cloud-tools-5.15.0"},
          {"reference": "linux-cloud-tools-common"},
          {"reference": "linux-doc"},
          {"reference": "linux-gcp-headers-5.15.0"},
          {"reference": "linux-gcp-tools-5.15.0"},
          {"reference": "linux-gke-headers-5.15.0"},
          {"reference": "linux-gke-tools-5.15.0"},
          {"reference": "linux-gkeop"},
          {"reference": "linux-headers-5.15.0"},
          {"reference": "linux-ibm-cloud-tools-5.15.0"},
          {"reference": "linux-ibm-cloud-tools-common"},
          {"reference": "linux-ibm-headers-5.15.0"},
          {"reference": "linux-ibm-source-5.15.0"},
          {"reference": "linux-ibm-tools-5.15.0"},
          {"reference": "linux-ibm-tools-common"},
          {"reference": "linux-image-5.15.0"},
          {"reference": "linux-image-unsigned-5.15.0"},
          {"reference": "linux-intel-iot-realtime"},
          {"reference": "linux-intel-iotg-cloud-tools-5.15.0"},
          {"reference": "linux-intel-iotg-cloud-tools-common"},
          {"reference": "linux-intel-iotg-headers-5.15.0"},
          {"reference": "linux-intel-iotg-tools-5.15.0"},
          {"reference": "linux-intel-iotg-tools-common"},
          {"reference": "linux-intel-iotg-tools-host"},
          {"reference": "linux-kvm-cloud-tools-5.15.0"},
          {"reference": "linux-kvm-headers-5.15.0"},
          {"reference": "linux-kvm-tools-5.15.0"},
          {"reference": "linux-libc-dev"},
          {"reference": "linux-lowlatency-cloud-tools-5.15.0"},
          {"reference": "linux-lowlatency-cloud-tools-common"},
          {"reference": "linux-lowlatency-headers-5.15.0"},
          {"reference": "linux-lowlatency-tools-5.15.0"},
          {"reference": "linux-lowlatency-tools-common"},
          {"reference": "linux-lowlatency-tools-host"},
          {"reference": "linux-modules-5.15.0"},
          {"reference": "linux-modules-extra-5.15.0"},
          {"reference": "linux-nvidia"},
          {"reference": "linux-nvidia-tegra"},
          {"reference": "linux-nvidia-tegra-igx"},
          {"reference": "linux-oracle-headers-5.15.0"},
          {"reference": "linux-oracle-tools-5.15.0"},
          {"reference": "linux-raspi-headers-5.15.0"},
          {"reference": "linux-raspi-tools-5.15.0"},
          {"reference": "linux-realtime"},
          {"reference": "linux-riscv-headers-5.15.0"},
          {"reference": "linux-riscv-tools-5.15.0"},
          {"reference": "linux-source-5.15.0"},
          {"reference": "linux-tools-5.15.0"},
          {"reference": "linux-tools-common"},
          {"reference": "linux-tools-host"},
          {"reference": "linux-udebs-aws"},
          {"reference": "linux-udebs-azure"},
          {"reference": "linux-xilinx-zynqmp"}
        ]
      }
    ]
  },
  "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');
}

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21 May 2026 00:00Current
6.7Medium risk
Vulners AI Score6.7
CVSS 21.9
CVSS 3.15.5
EPSS0.00113
linux vulnerabilitycve-2021-4095denial of servicekernel oopslocal attackerkvm flaw.
5