Log in Start free

Vulnerability · Published Mar 3, 2021 · Assigned by redhat

CVE-2021-20233

High 8.2

In plain English

A high-severity out-of-bounds write in grub2. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.6% (higher than 49% of all known vulnerabilities). Ready-made attack tooling exists: public proof-of-concept code. Fixed versions are available - upgrade the affected package.

Severity (CVSS NVD)8.2High
Exploit odds (30 days)0.6%top 50.8% of all CVEs
Exploited in the wildNo reportsnot in CISA KEV
Attack tooling1Public PoC

Official 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 packages & fixed versions

EcosystemPackageFixed inAdvisory
AlmaLinux:8shim-aa6415.4-2.el8_1.almaALSA-2021:1734
AlmaLinux:8shim-ia3215.4-2.el8_1.almaALSA-2021:1734
AlmaLinux:8shim-unsigned-aarch6415-7.el8_1.almaALSA-2021:1734
AlmaLinux:8shim-unsigned-x6415.4-4.el8_1.almaALSA-2021:1734
AlmaLinux:8shim-x6415.4-2.el8_1.almaALSA-2021:1734
Alpine:v3.20grub2.06-r0ALPINE-CVE-2021-20233
Alpine:v3.21grub2.06-r0ALPINE-CVE-2021-20233
Alpine:v3.22grub2.06-r0ALPINE-CVE-2021-20233
Alpine:v3.23grub2.06-r0ALPINE-CVE-2021-20233
Alpine:v3.24grub2.06-r0ALPINE-CVE-2021-20233
Debian:12grub22.04-16DEBIAN-CVE-2021-20233
Debian:13grub22.04-16DEBIAN-CVE-2021-20233
Debian:14grub22.04-16DEBIAN-CVE-2021-20233
Rocky Linux:8fwupd0:1.5.9-1.el8_4RLSA-2021:2566
Rocky Linux:8shim-unsigned-aarch640:15-7.el8.1.1RLSA-2021:1734

Affected products (as reported)

VendorProductVersions
n/a grub2 grub 2.06

Weakness: CWE-787

References