What’s Vulnerable › Vulnerabilities

CVE-2021-20233

• Severity: high (CVSS 8.2 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.6% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2021-03-03 · updated 2026-06-17
• Weakness: CWE-787

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.

Affected products

• Fedoraproject Fedora: 33, 34
• grub2: before 2.06 — fixed in 2.06
• NetApp ONTAP Select Deploy administration utility: all versions
• Red Hat Enterprise Linux: 7.0, 8.0
• RedHat Enterprise Linux Server Aus: 7.2, 7.3, 7.4, 7.6, 7.7, 8.2
• RedHat Enterprise Linux Server Eus: 7.6, 7.7, 8.1
• RedHat Enterprise Linux Server Tus: 7.4, 7.6, 7.7, 8.2
• RedHat Enterprise Linux Workstation: 7.0

How to fix

Upgrade to a fixed version: grub2 2.06. Check the vendor advisory for mitigations.

References

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

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