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Vulnerability record · CVE-2021-20233 · published 3 March 2021

CVE-2021-20233: Gnu grub2 out-of-bounds write vulnerability

Gnu · Grub2

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.

8.2 CVSS 3.1 High EPSS 0.61% · top 53.1% CWE-787 · Out-of-bounds write
8.2CVSS 3.1 base score, v2 7.2
0.61%EPSS exploitation probability, 30 days
NoNot in CISA KEV
8Affected product versions listed by NVD
8References
17 Jun 2026Last modified by NVD

Description

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.

CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:H

Affected products

8 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://bugzilla.redhat.com/show_bug.cgi?id=1926263 Issue TrackingPatchThird Party Advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/ZWZ36QK4IKU6MWDWNOOWKPH
https://security.gentoo.org/glsa/202104-05 Third Party Advisory
https://security.netapp.com/advisory/ntap-20220325-0001/ Third Party Advisory
https://bugzilla.redhat.com/show_bug.cgi?id=1926263 Issue TrackingPatchThird Party Advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/ZWZ36QK4IKU6MWDWNOOWKPH
https://security.gentoo.org/glsa/202104-05 Third Party Advisory
https://security.netapp.com/advisory/ntap-20220325-0001/ Third Party Advisory

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Source: NIST National Vulnerability Database (record CVE-2021-20233), CISA KEV, FIRST EPSS (scores of 2026-09-27). This page is refreshed as NVD updates the record.