CVE-2021-20233

Name: CVE-2021-20233
Creator: NVD / NIST
Published: 2021-03-03T17:15:12.037+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

HIGHCVSS 8.2/10EPSS 0.61%

Last modified Jun 17, 2026

CVE-2021-20233 is a high-severity vulnerability rated 8.2/10 on the CVSS scale. 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. EPSS estimates a 0.61% chance of exploitation in the next 30 days.

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.

Metrics

CVSS 3.1

8.2/10

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

EPSS Probability

0.61%

44.7th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

Vendor	Product	Versions
Gnu	Grub2	< 2.06
Redhat	Enterprise Linux	7.0
Redhat	Enterprise Linux	8.0
Redhat	Enterprise Linux Server Aus	7.2
Redhat	Enterprise Linux Server Aus	7.3
Redhat	Enterprise Linux Server Aus	7.4
Redhat	Enterprise Linux Server Aus	7.6
Redhat	Enterprise Linux Server Aus	7.7
Redhat	Enterprise Linux Server Aus	8.2
Redhat	Enterprise Linux Server Eus	7.6
Redhat	Enterprise Linux Server Eus	7.7
Redhat	Enterprise Linux Server Eus	8.1
Redhat	Enterprise Linux Server Tus	7.4
Redhat	Enterprise Linux Server Tus	7.6
Redhat	Enterprise Linux Server Tus	7.7
Redhat	Enterprise Linux Server Tus	8.2
Redhat	Enterprise Linux Workstation	7.0
Fedoraproject	Fedora	33
Fedoraproject	Fedora	34
Netapp	Ontap Select Deploy Administration Utility	All versions

References

https://bugzilla.redhat.com/show_bug.cgi?id=1926263Issue Tracking, Patch, Third Party Advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/ZWZ36QK4IKU6MWDWNOOWKPH3WXZBHT2R/
https://security.gentoo.org/glsa/202104-05Third Party Advisory
https://security.netapp.com/advisory/ntap-20220325-0001/Third Party Advisory
https://bugzilla.redhat.com/show_bug.cgi?id=1926263Issue Tracking, Patch, Third Party Advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/ZWZ36QK4IKU6MWDWNOOWKPH3WXZBHT2R/
https://security.gentoo.org/glsa/202104-05Third Party Advisory
https://security.netapp.com/advisory/ntap-20220325-0001/Third Party Advisory

Timeline

Published: Mar 3, 2021
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2021-20233?

How severe is CVE-2021-20233?

CVE-2021-20233 has a CVSS score of 8.2/10 (HIGH severity). The EPSS model estimates a 0.61% probability of exploitation in the next 30 days.

How do I fix CVE-2021-20233?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2021-20233?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST