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Fencer Vulns
high 8.2

CVE-2021-20233 json

A flaw was found in grub2 in versions prior to 2.06.

published 2021-03-03 5 y ago modified 2026-06-17 4 mo ago also EUVD-2021-7672

cvss
8.2
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
0.6%
EPSS 0.6% chance of exploitation in 30 days, percentile 49%
public exploits
0
none known

Summary

A flaw was found in grub2 in versions prior to 2.06. Setparam_prefix() in the menu rendering code performs a length calculation on the assumption that expressing a quoted single quote will require 3 characters, while it actually requires 4 characters which allows an attacker to corrupt memory by one byte for each quote in the input. The highest threat from this vulnerability is to data confidentiality and integrity as well as system availability.

Patch / fix

  • gnu grub2 2.06
  • grub2 Debian 14, Debian 13, Debian 12 2.04-16

debian advisories DEBIAN-CVE-2021-20233

  • grub2-signed Ubuntu 18.04 LTS 1.167~18.04.5
  • grub2-signed Ubuntu 20.04 LTS 1.167.2
  • grub2-unsigned Ubuntu 18.04 LTS 2.04-1ubuntu44.1.2
  • grub2-unsigned Ubuntu 20.04 LTS 2.04-1ubuntu44.2

ubuntu advisories UBUNTU-CVE-2021-20233

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • shim RHEL 8, RHEL 8.2 EUS, RHEL 8.1 EUS 15.4-2.el8_1
  • shim-x64 RHEL 8, RHEL 8.2 EUS, RHEL 8.1 EUS 15.4-2.el8_1
  • shim-aa64 RHEL 8, RHEL 8.2 EUS, RHEL 8.1 EUS 15.4-2.el8_1
  • shim-ia32 RHEL 8, RHEL 8.2 EUS, RHEL 8.1 EUS 15.4-2.el8_1
  • shim-unsigned-x64 RHEL 8, RHEL 8.2 EUS, RHEL 8.1 EUS 15.4-4.el8_1
  • shim-unsigned-aarch64 RHEL 8, RHEL 8.2 EUS, RHEL 8.1 EUS 15-7.el8_1
  • grub2 RHEL 7 1:2.02-0.87.el7_9.2
  • grub2-pc RHEL 7 1:2.02-0.87.el7_9.2

red hat advisories RHSA-2021:1734RHSA-2021:0701RHSA-2021:0699RHSA-2021:0700RHSA-2021:0704RHSA-2021:0703

  • grub2 SLES for SAP 15, SLES 15-LTSS, SLE High Performance Computing 15-LTSS +1 more 2.02-19.66.1
  • grub2 SLES for SAP 15 SP1, SLES 15 SP1-LTSS, SLES 15 SP1-BCL +6 more 2.02-26.43.1
  • grub2 SLE Module for Server Applications 15 SP2, SLE Module for Basesystem 15 SP2 2.04-9.34.1
  • grub2 SLES for SAP 12 SP3, SLES 12 SP3-LTSS, SLES 12 SP3-BCL +3 more 2.02-4.69.1
  • grub2 SLES for SAP 12 SP5, SLES for SAP 12 SP4, SLES 12 SP5 +3 more 2.02-12.47.1
  • grub2 SLES for SAP 12 SP2, SLES 12 SP2-LTSS, SLES 12 SP2-BCL +1 more 2.02-115.59.1
  • grub2 SLES 11 SP4-LTSS 2.02-0.66.26.1

suse advisories SUSE-SU-2021:0685-1SUSE-SU-2021:0684-1SUSE-SU-2021:0683-1SUSE-SU-2021:0682-1SUSE-SU-2021:0681-1SUSE-SU-2021:14659-1

  • grub2 openSUSE Tumbleweed 2.06-7.1
  • grub2 openSUSE Leap 15.2 2.04-lp152.7.22.7

opensuse advisories openSUSE-SU-2024:10824-1openSUSE-SU-2021:0462-1

  • shim-x64 AlmaLinux 8 15.4-2.el8_1.alma
  • shim-aa64 AlmaLinux 8 15.4-2.el8_1.alma
  • shim-ia32 AlmaLinux 8 15.4-2.el8_1.alma
  • shim-unsigned-x64 AlmaLinux 8 15.4-4.el8_1.alma
  • shim-unsigned-aarch64 AlmaLinux 8 15-7.el8_1.alma

almalinux advisories ALSA-2021:1734

  • fwupd Rocky Linux 8 1.5.9-1.el8_4
  • shim-unsigned-aarch64 Rocky Linux 8 15-7.el8.1.1

rocky linux advisories RLSA-2021:2566RLSA-2021:1734

  • grub Alpine 3.24, Alpine 3.23, Alpine 3.22 +5 more 2.06-r0

alpine advisories ALPINE-CVE-2021-20233

Alpine secdb © Alpine Linux, from https://secdb.alpinelinux.org via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • grub2 CBL-Mariner 2.0 2.06~rc1-7
  • grub2 Azure Linux 3.0 2.06-26

azure linux advisories AZL-6466AZL-78305

Azure Linux vulnerability data, Copyright (c) Microsoft Corporation, from https://github.com/microsoft/AzureLinuxVulnerabilityData via OSV, under the MIT licence; changed: normalised to fixed package versions per release. MIT

  • grub Arch Linux 2:2.06-1

arch linux advisories AVG-1629

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2021-20233 updated cvss 7.5

grub2: Heap out-of-bounds write due to miscalculation of space required for quoting

  • Red Hat Enterprise Linux 7 fwupd, fwupdate, fwupdate-efi, fwupdate-libs
    affected: no fix available
  • Red Hat CodeReady Linux Builder (v. 8) shim-unsigned-x64 15.4-4.el8_1, shim-unsigned-aarch64 15-7.el8_1
    fixed: vendor fix RHSA-2021:1734
  • Red Hat CodeReady Linux Builder EUS (v. 8.1) shim-unsigned-x64 15.4-4.el8_1, shim-unsigned-aarch64 15-7.el8_1
    fixed: vendor fix RHSA-2021:3675
  • Red Hat CodeReady Linux Builder EUS (v. 8.2) shim-unsigned-x64 15.4-4.el8_1, shim-unsigned-aarch64 15-7.el8_1
    fixed: vendor fix RHSA-2021:2790
  • Red Hat Enterprise Linux BaseOS (v. 8) shim 15.4-2.el8_1, fwupd 1.5.9-1.el8_4, grub2 2.02-90.el8_3.1, shim-x64 15.4-2.el8_1, shim-aa64 15.4-2.el8_1, shim-ia32 15.4-2.el8_1, +18 more
    fixed: vendor fix RHSA-2021:0696
  • Red Hat Enterprise Linux BaseOS EUS (v. 8.1) shim 15.4-2.el8_1, fwupd 1.1.4-4.el8_1, grub2 2.02-87.el8_1.2, shim-x64 15.4-2.el8_1, shim-aa64 15.4-2.el8_1, shim-ia32 15.4-2.el8_1, +18 more
    fixed: vendor fix RHSA-2021:3675
  • Red Hat Enterprise Linux BaseOS EUS (v. 8.2) shim 15.4-2.el8_1, fwupd 1.1.4-9.el8_2, grub2 2.02-87.el8_2.3, shim-x64 15.4-2.el8_1, shim-aa64 15.4-2.el8_1, shim-ia32 15.4-2.el8_1, +18 more
    fixed: vendor fix RHSA-2021:2790
  • Red Hat Enterprise Linux Client (v. 7) grub2 2.02-0.87.el7_9.2, grub2-pc 2.02-0.87.el7_9.2, grub2-tools 2.02-0.87.el7_9.2, grub2-common 2.02-0.87.el7_9.2, grub2-efi-x64 2.02-0.87.el7_9.2, grub2-efi-ia32 2.02-0.87.el7_9.2, +5 more Red Hat Enterprise Linux Client Optional (v. 7) grub2-ppc-modules 2.02-0.87.el7_9.2, grub2-ppc64-modules 2.02-0.87.el7_9.2, grub2-efi-x64-cdboot 2.02-0.87.el7_9.2, grub2-efi-ia32-cdboot 2.02-0.87.el7_9.2, grub2-ppc64le-modules 2.02-0.87.el7_9.2, grub2-efi-aa64-modules 2.02-0.87.el7_9.2
    fixed: vendor fix RHSA-2021:0699
show 21 more
  • Red Hat Enterprise Linux ComputeNode EUS (v. 7.6) grub2 2.02-0.86.el7_6.3, grub2-pc 2.02-0.86.el7_6.3, grub2-tools 2.02-0.86.el7_6.3, grub2-common 2.02-0.86.el7_6.3, grub2-efi-x64 2.02-0.86.el7_6.3, grub2-efi-ia32 2.02-0.86.el7_6.3, +5 more
    fixed: vendor fix RHSA-2021:0701
  • Red Hat Enterprise Linux ComputeNode EUS (v. 7.7) grub2 2.02-0.86.el7_7.3, grub2-pc 2.02-0.86.el7_7.3, grub2-tools 2.02-0.86.el7_7.3, grub2-common 2.02-0.86.el7_7.3, grub2-efi-x64 2.02-0.86.el7_7.3, grub2-efi-ia32 2.02-0.86.el7_7.3, +5 more
    fixed: vendor fix RHSA-2021:0700
  • Red Hat Enterprise Linux ComputeNode Optional (v. 7) grub2-ppc-modules 2.02-0.87.el7_9.2, grub2-ppc64-modules 2.02-0.87.el7_9.2, grub2-efi-x64-cdboot 2.02-0.87.el7_9.2, grub2-efi-ia32-cdboot 2.02-0.87.el7_9.2, grub2-ppc64le-modules 2.02-0.87.el7_9.2, grub2-efi-aa64-modules 2.02-0.87.el7_9.2
    fixed: vendor fix RHSA-2021:0699
  • Red Hat Enterprise Linux ComputeNode Optional EUS (v. 7.6) grub2-ppc-modules 2.02-0.86.el7_6.3, grub2-ppc64-modules 2.02-0.86.el7_6.3, grub2-efi-x64-cdboot 2.02-0.86.el7_6.3, grub2-efi-ia32-cdboot 2.02-0.86.el7_6.3, grub2-ppc64le-modules 2.02-0.86.el7_6.3, grub2-efi-aa64-modules 2.02-0.86.el7_6.3
    fixed: vendor fix RHSA-2021:0701
  • Red Hat Enterprise Linux ComputeNode Optional EUS (v. 7.7) grub2-ppc-modules 2.02-0.86.el7_7.3, grub2-ppc64-modules 2.02-0.86.el7_7.3, grub2-efi-x64-cdboot 2.02-0.86.el7_7.3, grub2-efi-ia32-cdboot 2.02-0.86.el7_7.3, grub2-ppc64le-modules 2.02-0.86.el7_7.3, grub2-efi-aa64-modules 2.02-0.86.el7_7.3
    fixed: vendor fix RHSA-2021:0700
  • Red Hat Enterprise Linux for ARM and IBM Power LE (POWER9) Server (v. 7) grub2 2.02-0.86.el7_6.3, grub2-tools 2.02-0.86.el7_6.3, grub2-common 2.02-0.86.el7_6.3, grub2-ppc64le 2.02-0.86.el7_6.3, grub2-tools-extra 2.02-0.86.el7_6.3, grub2-tools-minimal 2.02-0.86.el7_6.3, +1 more Red Hat Enterprise Linux for ARM and IBM Power LE (POWER9) Server Optional (v. 7) grub2-pc-modules 2.02-0.86.el7_6.3, grub2-ppc-modules 2.02-0.86.el7_6.3, grub2-ppc64-modules 2.02-0.86.el7_6.3, grub2-efi-x64-modules 2.02-0.86.el7_6.3, grub2-efi-aa64-modules 2.02-0.86.el7_6.3, grub2-efi-ia32-modules 2.02-0.86.el7_6.3
    fixed: vendor fix RHSA-2021:0701
  • Red Hat Enterprise Linux Server (v. 7) grub2 2.02-0.87.el7_9.2, grub2-pc 2.02-0.87.el7_9.2, grub2-ppc64 2.02-0.87.el7_9.2, grub2-tools 2.02-0.87.el7_9.2, grub2-common 2.02-0.87.el7_9.2, grub2-efi-x64 2.02-0.87.el7_9.2, +9 more
    fixed: vendor fix RHSA-2021:0699
  • Red Hat Enterprise Linux Server AUS (v. 7.2) grub2 2.02-0.86.el7_2.2, grub2-pc 2.02-0.86.el7_2.2, grub2-tools 2.02-0.86.el7_2.2, grub2-common 2.02-0.86.el7_2.2, grub2-efi-x64 2.02-0.86.el7_2.2, grub2-efi-ia32 2.02-0.86.el7_2.2, +7 more
    fixed: vendor fix RHSA-2021:0704
  • Red Hat Enterprise Linux Server AUS (v. 7.3) grub2 2.02-0.86.el7_3.2, grub2-pc 2.02-0.86.el7_3.2, grub2-tools 2.02-0.86.el7_3.2, grub2-common 2.02-0.86.el7_3.2, grub2-efi-x64 2.02-0.86.el7_3.2, grub2-efi-ia32 2.02-0.86.el7_3.2, +8 more
    fixed: vendor fix RHSA-2021:0703
  • Red Hat Enterprise Linux Server AUS (v. 7.4) grub2 2.02-0.86.el7_4.2, grub2-pc 2.02-0.86.el7_4.2, grub2-tools 2.02-0.86.el7_4.2, grub2-common 2.02-0.86.el7_4.2, grub2-efi-x64 2.02-0.86.el7_4.2, grub2-efi-ia32 2.02-0.86.el7_4.2, +5 more Red Hat Enterprise Linux Server E4S (v. 7.4) grub2 2.02-0.86.el7_4.2, grub2-pc 2.02-0.86.el7_4.2, grub2-tools 2.02-0.86.el7_4.2, grub2-common 2.02-0.86.el7_4.2, grub2-efi-x64 2.02-0.86.el7_4.2, grub2-ppc64le 2.02-0.86.el7_4.2, +7 more
    fixed: vendor fix RHSA-2021:0702
  • Red Hat Enterprise Linux Server EUS (v. 7.6) grub2 2.02-0.86.el7_6.3, grub2-pc 2.02-0.86.el7_6.3, grub2-ppc64 2.02-0.86.el7_6.3, grub2-tools 2.02-0.86.el7_6.3, grub2-common 2.02-0.86.el7_6.3, grub2-efi-x64 2.02-0.86.el7_6.3, +9 more
    fixed: vendor fix RHSA-2021:0701
  • Red Hat Enterprise Linux Server EUS (v. 7.7) grub2 2.02-0.86.el7_7.3, grub2-pc 2.02-0.86.el7_7.3, grub2-ppc64 2.02-0.86.el7_7.3, grub2-tools 2.02-0.86.el7_7.3, grub2-common 2.02-0.86.el7_7.3, grub2-efi-x64 2.02-0.86.el7_7.3, +9 more
    fixed: vendor fix RHSA-2021:0700
  • Red Hat Enterprise Linux Server Optional (v. 7) grub2-pc-modules 2.02-0.87.el7_9.2, grub2-ppc-modules 2.02-0.87.el7_9.2, grub2-ppc64-modules 2.02-0.87.el7_9.2, grub2-efi-x64-cdboot 2.02-0.87.el7_9.2, grub2-efi-ia32-cdboot 2.02-0.87.el7_9.2, grub2-efi-x64-modules 2.02-0.87.el7_9.2, +3 more
    fixed: vendor fix RHSA-2021:0699
  • Red Hat Enterprise Linux Server Optional AUS (v. 7.2) grub2 2.02-0.86.el7_2.2, grub2-pc-modules 2.02-0.86.el7_2.2, grub2-ppc-modules 2.02-0.86.el7_2.2, grub2-ppc64-modules 2.02-0.86.el7_2.2, grub2-efi-x64-cdboot 2.02-0.86.el7_2.2, grub2-efi-ia32-cdboot 2.02-0.86.el7_2.2, +4 more
    fixed: vendor fix RHSA-2021:0704
  • Red Hat Enterprise Linux Server Optional AUS (v. 7.3) grub2 2.02-0.86.el7_3.2, grub2-pc 2.02-0.86.el7_3.2, grub2-tools 2.02-0.86.el7_3.2, grub2-common 2.02-0.86.el7_3.2, grub2-efi-x64 2.02-0.86.el7_3.2, grub2-efi-ia32 2.02-0.86.el7_3.2, +11 more
    fixed: vendor fix RHSA-2021:0703
  • Red Hat Enterprise Linux Server Optional AUS (v. 7.4) grub2-ppc-modules 2.02-0.86.el7_4.2, grub2-ppc64-modules 2.02-0.86.el7_4.2, grub2-efi-x64-cdboot 2.02-0.86.el7_4.2, grub2-efi-ia32-cdboot 2.02-0.86.el7_4.2, grub2-ppc64le-modules 2.02-0.86.el7_4.2, grub2-efi-aa64-modules 2.02-0.86.el7_4.2 Red Hat Enterprise Linux Server Optional E4S (v. 7.4) grub2-pc-modules 2.02-0.86.el7_4.2, grub2-ppc-modules 2.02-0.86.el7_4.2, grub2-ppc64-modules 2.02-0.86.el7_4.2, grub2-efi-x64-cdboot 2.02-0.86.el7_4.2, grub2-efi-ia32-cdboot 2.02-0.86.el7_4.2, grub2-efi-x64-modules 2.02-0.86.el7_4.2, +3 more
    fixed: vendor fix RHSA-2021:0702
  • Red Hat Enterprise Linux Server Optional EUS (v. 7.6) grub2-pc-modules 2.02-0.86.el7_6.3, grub2-ppc-modules 2.02-0.86.el7_6.3, grub2-ppc64-modules 2.02-0.86.el7_6.3, grub2-efi-x64-cdboot 2.02-0.86.el7_6.3, grub2-efi-ia32-cdboot 2.02-0.86.el7_6.3, grub2-efi-x64-modules 2.02-0.86.el7_6.3, +3 more
    fixed: vendor fix RHSA-2021:0701
  • Red Hat Enterprise Linux Server Optional EUS (v. 7.7) grub2-pc-modules 2.02-0.86.el7_7.3, grub2-ppc-modules 2.02-0.86.el7_7.3, grub2-ppc64-modules 2.02-0.86.el7_7.3, grub2-efi-x64-cdboot 2.02-0.86.el7_7.3, grub2-efi-ia32-cdboot 2.02-0.86.el7_7.3, grub2-efi-x64-modules 2.02-0.86.el7_7.3, +3 more
    fixed: vendor fix RHSA-2021:0700
  • Red Hat Enterprise Linux Server Optional TUS (v. 7.4) grub2-ppc-modules 2.02-0.86.el7_4.2, grub2-ppc64-modules 2.02-0.86.el7_4.2, grub2-efi-x64-cdboot 2.02-0.86.el7_4.2, grub2-efi-ia32-cdboot 2.02-0.86.el7_4.2, grub2-ppc64le-modules 2.02-0.86.el7_4.2, grub2-efi-aa64-modules 2.02-0.86.el7_4.2 Red Hat Enterprise Linux Server TUS (v. 7.4) grub2 2.02-0.86.el7_4.2, grub2-pc 2.02-0.86.el7_4.2, grub2-tools 2.02-0.86.el7_4.2, grub2-common 2.02-0.86.el7_4.2, grub2-efi-x64 2.02-0.86.el7_4.2, grub2-efi-ia32 2.02-0.86.el7_4.2, +5 more
    fixed: vendor fix RHSA-2021:0702
  • Red Hat Enterprise Linux Workstation (v. 7) grub2 2.02-0.87.el7_9.2, grub2-pc 2.02-0.87.el7_9.2, grub2-tools 2.02-0.87.el7_9.2, grub2-common 2.02-0.87.el7_9.2, grub2-efi-x64 2.02-0.87.el7_9.2, grub2-efi-ia32 2.02-0.87.el7_9.2, +5 more Red Hat Enterprise Linux Workstation Optional (v. 7) grub2-ppc-modules 2.02-0.87.el7_9.2, grub2-ppc64-modules 2.02-0.87.el7_9.2, grub2-efi-x64-cdboot 2.02-0.87.el7_9.2, grub2-efi-ia32-cdboot 2.02-0.87.el7_9.2, grub2-ppc64le-modules 2.02-0.87.el7_9.2, grub2-efi-aa64-modules 2.02-0.87.el7_9.2
    fixed: vendor fix RHSA-2021:0699
  • Red Hat Enterprise Linux 7 shim, mokutil, shim-unsigned, shim-unsigned-x64, shim-unsigned-ia32
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

cisa ICSA-21-336-06 updated cvss 8.2

Hitachi Energy APM Edge

  • Hitachi Energy APM Edge 3.0, 2.0, 1.0
    affected: vendor fix, mitigation “Physically protect process control systems from direct access by unauthorized personnel.” search.abb.com

From CISA ICS and IT advisories (CSAF, https://github.com/cisagov/CSAF), a U.S. Government work; changed: reduced to products, statuses and remediations. CISA notification · csaf

Exploit prediction

0.60% chance of exploitation in the next 30 days, higher than 49% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
NVD 3.1 8.2 CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:H
NVD 2.0 7.2 AV:L/AC:L/Au:N/C:C/I:C/A:C

Affected products

  • n/a grub2

Classification

Weakness

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.