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Grub2Application · Gnu

CVE-2022-28736

HIGH · 7.8 CVSS v3.1 Published 2023-07-20
Fix available
A fix is available. Upgrade to 2.06-3 or later.
See remediation →
80/100
Remediation priority · High
Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
There's a use-after-free vulnerability in grub_cmd_chainloader() function; The chainloader command is used to boot up operating systems that doesn't support multiboot and do not have direct support from GRUB2. When executing chainloader more than once a use-after-free vulnerability is triggered. If an attacker can control the GRUB2's memory allocation pattern sensitive data may be exposed and arbitrary code execution can be achieved.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · moderate confidence

A use-after-free vulnerability exists in GRUB2's grub_cmd_chainloader() function. When the chainloader command is executed multiple times, memory is freed but continues to be referenced, creating a use-after-free condition. An attacker with control over GRUB2's memory allocation patterns could exploit this to expose sensitive data from freed memory regions and achieve arbitrary code execution.

MitigationUpdate GRUB2 to the patched version that addresses this use-after-free vulnerability. Restrict physical access to systems to prevent unauthorized attackers from repeatedly executing the chainloader command.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Grub2Application
Affected:>= 2.00, < 2.06-3

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Local
Complexity
Low
Privileges
Low
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

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

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify GRUB2 version
    Run 'grub-install --version' or check your distribution's package manager for the grub2 or grub-pc package version (e.g., dpkg -l grub-pc, rpm -qa grub2)
    Affected if Version is greater than or equal to 2.00 and less than 2.06-3
  2. Verify chainloader command exists
    Check if the chainloader command is available in your GRUB2 installation; this is typically present in standard GRUB2 builds used for boot loader purposes
    Affected if The chainloader command is present and executable within GRUB2
  3. Confirm boot configuration uses GRUB2
    Verify the system boots using GRUB2 by checking for /boot/grub or /boot/grub2 directories, or by observing the boot loader menu at system startup
    Affected if The system uses GRUB2 as its boot loader

Your system is potentially affected if GRUB2 version is 2.00 or higher but below 2.06-3, the chainloader command is present, and GRUB2 is used as the boot loader.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 2.06-3 or later
Fixed in 2.06-3
Interim mitigation

Update GRUB2 to the patched version that addresses this use-after-free vulnerability. Restrict physical access to systems to prevent unauthorized attackers from repeatedly executing the chainloader command.

Recommended fix High confidence

GRUB2 version 2.06-3 or later

  1. 1. Identify the current GRUB2 version installed on the system using 'grub-install --version' or checking the package manager
  2. 2. If the version is >= 2.00 and < 2.06-3, plan for an upgrade
  3. 3. Update the system package repository to ensure latest packages are available
  4. 4. Upgrade GRUB2 package using the appropriate package manager (e.g., 'apt-get update && apt-get install grub2' for Debian/Ubuntu, or 'yum update grub2' for RHEL/CentOS)
  5. 5. After upgrading, regenerate GRUB configuration files using 'grub-mkconfig -o /boot/grub/grub.cfg'
  6. 6. Reboot the system to ensure the new GRUB2 version is loaded
Caveat Minimal risk; this is a security patch release. However, custom GRUB configurations should be backed up before regeneration of config files.

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Grub2 Scoped from the published advisory
  • Consultation3.0 h
  • Implementation4.0 h
  • Testing3.0 h
  • Review / QA2.0 h
12.0 hours of engineering $2,130
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $3,408.

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2022-28736 in production — separate from our analysis above.

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data