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Linux Distros Unpatched Vulnerability : CVE-2021-20255

🗓️ 04 Mar 2025 00:00:00Reported by TenableType 
nessus
 nessus🔗 www.tenable.com👁 12 Views

Linux distributions have unpatched CVE-2021-20255 vulnerability affecting system availability and performance.

Related
Refs
Code
ReporterTitlePublishedViews
Family
AlpineLinux		CVE-2021-20255
9 Mar 202119:14
–alpinelinux
AstraLinux		Astra Linux – Vulnerability in Qemu
3 May 202623:59
–astralinux
BDU FSTEC		The vulnerability of the eepro100 i8255x hardware emulation software by QEMU allows a hacker to induce a service failure.
12 Sep 202200:00
–bdu_fstec
CBLMariner		CVE-2021-20255 affecting package qemu for versions less than 6.2.0-18
22 Apr 202515:08
–cbl_mariner
CBLMariner		CVE-2021-20255 affecting package qemu-kvm 4.2.0-48
6 Apr 202123:50
–cbl_mariner
CBLMariner		CVE-2021-20255 affecting package qemu for versions less than 6.2.0-2
3 Jun 202217:54
–cbl_mariner
Circl		CVE-2021-20255
9 Mar 202122:52
–circl
CNNVD		QEMU Security Vulnerabilities
25 Feb 202100:00
–cnnvd
CVE		CVE-2021-20255
9 Mar 202119:14
–cve
Cvelist		CVE-2021-20255
9 Mar 202119:14
–cvelist
Rows per page
#%NASL_MIN_LEVEL 80900
##
# (C) Tenable, Inc.
##

include('compat.inc');

if (description)
{
  script_id(223690);
  script_version("1.8");
  script_set_attribute(attribute:"plugin_modification_date", value:"2026/06/01");

  script_cve_id("CVE-2021-20255");

  script_name(english:"Linux Distros Unpatched Vulnerability : CVE-2021-20255");

  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 stack overflow via an infinite recursion vulnerability was found in the eepro100 i8255x device emulator
    of QEMU. This issue occurs while processing controller commands due to a DMA reentry issue. This flaw
    allows a guest user or process to consume CPU cycles or crash the QEMU process on the host, resulting in a
    denial of service. The highest threat from this vulnerability is to system availability. (CVE-2021-20255)

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-2021-20255");
  script_set_attribute(attribute:"see_also", value:"https://ubuntu.com/security/CVE-2021-20255");
  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:U/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-2021-20255");

  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:"2020/12/03");
  script_set_attribute(attribute:"plugin_publication_date", value:"2025/03/04");

  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:"cpe:/o:canonical:ubuntu_linux:25.04");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:canonical:ubuntu_linux:25.10");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:canonical:ubuntu_linux:26.04:-:lts");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:debian:debian_linux:11.0");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:debian:debian_linux:12.0");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:qemu");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:debian:debian_linux:qemu");
  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("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/Debian Linux-11", "Host/OS/Debian Linux-12", "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", "Host/OS/Ubuntu Linux-25.04", "Host/OS/Ubuntu Linux-25.10", "Host/OS/Ubuntu Linux-26.04");

  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 = {
  "Debian Linux-12": {
    "package_manager": "dpkg-l",
    "constraints": [
      {
        "release": "12",
        "pkgs": [
          {"reference": "qemu-block-extra"},
          {"reference": "qemu-guest-agent"},
          {"reference": "qemu-system"},
          {"reference": "qemu-system-arm"},
          {"reference": "qemu-system-common"},
          {"reference": "qemu-system-data"},
          {"reference": "qemu-system-gui"},
          {"reference": "qemu-system-mips"},
          {"reference": "qemu-system-misc"},
          {"reference": "qemu-system-ppc"},
          {"reference": "qemu-system-sparc"},
          {"reference": "qemu-system-x86"},
          {"reference": "qemu-system-xen"},
          {"reference": "qemu-user"},
          {"reference": "qemu-user-binfmt"},
          {"reference": "qemu-user-static"},
          {"reference": "qemu-utils"}
        ]
      }
    ]
  },
  "Debian Linux-11": {
    "package_manager": "dpkg-l",
    "constraints": [
      {
        "release": "11",
        "pkgs": [
          {"reference": "qemu"},
          {"reference": "qemu-block-extra"},
          {"reference": "qemu-guest-agent"},
          {"reference": "qemu-system"},
          {"reference": "qemu-system-arm"},
          {"reference": "qemu-system-common"},
          {"reference": "qemu-system-data"},
          {"reference": "qemu-system-gui"},
          {"reference": "qemu-system-mips"},
          {"reference": "qemu-system-misc"},
          {"reference": "qemu-system-ppc"},
          {"reference": "qemu-system-sparc"},
          {"reference": "qemu-system-x86"},
          {"reference": "qemu-user"},
          {"reference": "qemu-user-binfmt"},
          {"reference": "qemu-user-static"},
          {"reference": "qemu-utils"}
        ]
      }
    ]
  },
  "Ubuntu Linux-14.04": {
    "package_manager": "dpkg-l",
    "constraints": [
      {
        "release": "14.04",
        "pkgs": [
          {"reference": "qemu"},
          {"reference": "qemu-common"},
          {"reference": "qemu-guest-agent"},
          {"reference": "qemu-keymaps"},
          {"reference": "qemu-kvm"},
          {"reference": "qemu-system"},
          {"reference": "qemu-system-aarch64"},
          {"reference": "qemu-system-arm"},
          {"reference": "qemu-system-common"},
          {"reference": "qemu-system-mips"},
          {"reference": "qemu-system-misc"},
          {"reference": "qemu-system-ppc"},
          {"reference": "qemu-system-sparc"},
          {"reference": "qemu-system-x86"},
          {"reference": "qemu-user"},
          {"reference": "qemu-user-static"},
          {"reference": "qemu-utils"}
        ]
      }
    ]
  },
  "Ubuntu Linux-16.04": {
    "package_manager": "dpkg-l",
    "constraints": [
      {
        "release": "16.04",
        "pkgs": [
          {"reference": "qemu"},
          {"reference": "qemu-block-extra"},
          {"reference": "qemu-guest-agent"},
          {"reference": "qemu-kvm"},
          {"reference": "qemu-system"},
          {"reference": "qemu-system-aarch64"},
          {"reference": "qemu-system-arm"},
          {"reference": "qemu-system-common"},
          {"reference": "qemu-system-mips"},
          {"reference": "qemu-system-misc"},
          {"reference": "qemu-system-ppc"},
          {"reference": "qemu-system-s390x"},
          {"reference": "qemu-system-sparc"},
          {"reference": "qemu-system-x86"},
          {"reference": "qemu-user"},
          {"reference": "qemu-user-binfmt"},
          {"reference": "qemu-user-static"},
          {"reference": "qemu-utils"}
        ]
      }
    ]
  },
  "Ubuntu Linux-18.04": {
    "package_manager": "dpkg-l",
    "constraints": [
      {
        "release": "18.04",
        "pkgs": [
          {"reference": "qemu"},
          {"reference": "qemu-block-extra"},
          {"reference": "qemu-guest-agent"},
          {"reference": "qemu-kvm"},
          {"reference": "qemu-system"},
          {"reference": "qemu-system-arm"},
          {"reference": "qemu-system-common"},
          {"reference": "qemu-system-mips"},
          {"reference": "qemu-system-misc"},
          {"reference": "qemu-system-ppc"},
          {"reference": "qemu-system-s390x"},
          {"reference": "qemu-system-sparc"},
          {"reference": "qemu-system-x86"},
          {"reference": "qemu-user"},
          {"reference": "qemu-user-binfmt"},
          {"reference": "qemu-user-static"},
          {"reference": "qemu-utils"}
        ]
      }
    ]
  },
  "Ubuntu Linux-20.04": {
    "package_manager": "dpkg-l",
    "constraints": [
      {
        "release": "20.04",
        "pkgs": [
          {"reference": "qemu"},
          {"reference": "qemu-block-extra"},
          {"reference": "qemu-guest-agent"},
          {"reference": "qemu-kvm"},
          {"reference": "qemu-system"},
          {"reference": "qemu-system-arm"},
          {"reference": "qemu-system-common"},
          {"reference": "qemu-system-data"},
          {"reference": "qemu-system-gui"},
          {"reference": "qemu-system-mips"},
          {"reference": "qemu-system-misc"},
          {"reference": "qemu-system-ppc"},
          {"reference": "qemu-system-s390x"},
          {"reference": "qemu-system-sparc"},
          {"reference": "qemu-system-x86"},
          {"reference": "qemu-system-x86-microvm"},
          {"reference": "qemu-system-x86-xen"},
          {"reference": "qemu-user"},
          {"reference": "qemu-user-binfmt"},
          {"reference": "qemu-user-static"},
          {"reference": "qemu-utils"}
        ]
      }
    ]
  },
  "Ubuntu Linux-22.04": {
    "package_manager": "dpkg-l",
    "constraints": [
      {
        "release": "22.04",
        "pkgs": [
          {"reference": "qemu"},
          {"reference": "qemu-block-extra"},
          {"reference": "qemu-guest-agent"},
          {"reference": "qemu-system"},
          {"reference": "qemu-system-arm"},
          {"reference": "qemu-system-common"},
          {"reference": "qemu-system-data"},
          {"reference": "qemu-system-gui"},
          {"reference": "qemu-system-mips"},
          {"reference": "qemu-system-misc"},
          {"reference": "qemu-system-ppc"},
          {"reference": "qemu-system-s390x"},
          {"reference": "qemu-system-sparc"},
          {"reference": "qemu-system-x86"},
          {"reference": "qemu-system-x86-microvm"},
          {"reference": "qemu-system-x86-xen"},
          {"reference": "qemu-user"},
          {"reference": "qemu-user-binfmt"},
          {"reference": "qemu-user-static"},
          {"reference": "qemu-utils"}
        ]
      }
    ]
  },
  "Ubuntu Linux-24.04": {
    "package_manager": "dpkg-l",
    "constraints": [
      {
        "release": "24.04",
        "pkgs": [
          {"reference": "qemu-block-extra"},
          {"reference": "qemu-block-supplemental"},
          {"reference": "qemu-guest-agent"},
          {"reference": "qemu-system"},
          {"reference": "qemu-system-arm"},
          {"reference": "qemu-system-common"},
          {"reference": "qemu-system-data"},
          {"reference": "qemu-system-gui"},
          {"reference": "qemu-system-mips"},
          {"reference": "qemu-system-misc"},
          {"reference": "qemu-system-modules-opengl"},
          {"reference": "qemu-system-modules-spice"},
          {"reference": "qemu-system-ppc"},
          {"reference": "qemu-system-s390x"},
          {"reference": "qemu-system-sparc"},
          {"reference": "qemu-system-x86"},
          {"reference": "qemu-system-x86-xen"},
          {"reference": "qemu-system-xen"},
          {"reference": "qemu-user"},
          {"reference": "qemu-user-binfmt"},
          {"reference": "qemu-user-static"},
          {"reference": "qemu-utils"}
        ]
      }
    ]
  },
  "Ubuntu Linux-25.10": {
    "package_manager": "dpkg-l",
    "constraints": [
      {
        "release": "25.10",
        "pkgs": [
          {"reference": "qemu-block-extra"},
          {"reference": "qemu-block-supplemental"},
          {"reference": "qemu-guest-agent"},
          {"reference": "qemu-system"},
          {"reference": "qemu-system-arm"},
          {"reference": "qemu-system-common"},
          {"reference": "qemu-system-data"},
          {"reference": "qemu-system-gui"},
          {"reference": "qemu-system-mips"},
          {"reference": "qemu-system-misc"},
          {"reference": "qemu-system-modules-opengl"},
          {"reference": "qemu-system-modules-spice"},
          {"reference": "qemu-system-ppc"},
          {"reference": "qemu-system-riscv"},
          {"reference": "qemu-system-s390x"},
          {"reference": "qemu-system-sparc"},
          {"reference": "qemu-system-x86"},
          {"reference": "qemu-system-x86-xen"},
          {"reference": "qemu-system-xen"},
          {"reference": "qemu-user"},
          {"reference": "qemu-user-binfmt"},
          {"reference": "qemu-utils"}
        ]
      }
    ]
  },
  "Ubuntu Linux-26.04": {
    "package_manager": "dpkg-l",
    "constraints": [
      {
        "release": "26.04",
        "pkgs": [
          {"reference": "qemu-block-extra"},
          {"reference": "qemu-block-supplemental"},
          {"reference": "qemu-guest-agent"},
          {"reference": "qemu-system"},
          {"reference": "qemu-system-arm"},
          {"reference": "qemu-system-common"},
          {"reference": "qemu-system-data"},
          {"reference": "qemu-system-gui"},
          {"reference": "qemu-system-mips"},
          {"reference": "qemu-system-misc"},
          {"reference": "qemu-system-modules-opengl"},
          {"reference": "qemu-system-modules-spice"},
          {"reference": "qemu-system-ppc"},
          {"reference": "qemu-system-riscv"},
          {"reference": "qemu-system-s390x"},
          {"reference": "qemu-system-sparc"},
          {"reference": "qemu-system-x86"},
          {"reference": "qemu-system-x86-xen"},
          {"reference": "qemu-system-xen"},
          {"reference": "qemu-user"},
          {"reference": "qemu-user-binfmt"},
          {"reference": "qemu-utils"},
          {"reference": "ubuntu-virt"}
        ]
      }
    ]
  },
  "Ubuntu Linux-25.04": {
    "package_manager": "dpkg-l",
    "constraints": [
      {
        "release": "25.04",
        "pkgs": [
          {"reference": "qemu-block-extra"},
          {"reference": "qemu-block-supplemental"},
          {"reference": "qemu-guest-agent"},
          {"reference": "qemu-system"},
          {"reference": "qemu-system-arm"},
          {"reference": "qemu-system-common"},
          {"reference": "qemu-system-data"},
          {"reference": "qemu-system-gui"},
          {"reference": "qemu-system-mips"},
          {"reference": "qemu-system-misc"},
          {"reference": "qemu-system-modules-opengl"},
          {"reference": "qemu-system-modules-spice"},
          {"reference": "qemu-system-ppc"},
          {"reference": "qemu-system-riscv"},
          {"reference": "qemu-system-s390x"},
          {"reference": "qemu-system-sparc"},
          {"reference": "qemu-system-x86"},
          {"reference": "qemu-system-x86-xen"},
          {"reference": "qemu-system-xen"},
          {"reference": "qemu-user"},
          {"reference": "qemu-user-binfmt"},
          {"reference": "qemu-user-static"},
          {"reference": "qemu-utils"}
        ]
      }
    ]
  }
};

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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01 Jun 2026 00:00Current
6.4Medium risk
Vulners AI Score6.4
CVSS 22.1
CVSS 3.15.5
EPSS0.00411
linux distributionsunpatched vulnerabilitycve-2021-20255stack overflowdenial of serviceqemusystem availability
12