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Enterprise LinuxOperating system · Redhat

CVE-2023-4001

MEDIUM · 6.8 CVSS v3.1 Published 2024-01-15
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
73/100
Remediation priority · Elevated
No privileges 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
An authentication bypass flaw was found in GRUB due to the way that GRUB uses the UUID of a device to search for the configuration file that contains the password hash for the GRUB password protection feature. An attacker capable of attaching an external drive such as a USB stick containing a file system with a duplicate UUID (the same as in the "/boot/" file system) can bypass the GRUB password protection feature on UEFI systems, which enumerate removable drives before non-removable ones. This issue was introduced in a downstream patch in Red Hat's version of grub2 and does not affect the upstream package.

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 · high confidence

GRUB uses UUID to locate its configuration file containing password hashes for authentication. An attacker can attach a USB drive with a duplicate UUID matching the /boot/ filesystem; on UEFI systems that enumerate removable drives before non-removable ones, GRUB loads the config from the attacker's USB instead of the legitimate /boot/ location, bypassing password protection.

MitigationConfigure UEFI/BIOS to disable booting from removable devices, enforce boot order to prioritize internal storage, and enable Secure Boot with signed bootloaders to prevent unauthorized GRUB configuration loading.

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
Enterprise LinuxOperating system
Affected:= 9.0
FedoraOperating system
Affected:= 38= 39
Grub2Application
Affected:all versions

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
Physical
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:P/AC:L/PR:N/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. Verify UEFI boot mode is in use
    Check for the presence of /sys/firmware/efi directory. On Linux, run: ls -d /sys/firmware/efi
    Affected if The directory exists, indicating UEFI boot mode. Systems using legacy BIOS are not affected by this specific attack vector.
  2. Check if GRUB uses UUID to locate configuration
    Examine the GRUB configuration file (typically /boot/grub2/grub.cfg or /boot/efi/EFI/*/grub.cfg) for lines containing 'search' with '--no-floppy' and '--uuid' or '--fs-uuid' parameters.
    Affected if The configuration contains UUID-based search commands for locating the config file. This is the default behavior in affected GRUB versions.
  3. Determine if removable device boot is prioritized in UEFI boot order
    Access UEFI/BIOS settings and review the boot order sequence. Look for removable/USB devices listed before internal HDD/SSD. From Linux, check: efibootmgr -v (if efibootmgr is available) to see current boot entries.
    Affected if Removable/USB devices appear before internal storage in the boot order, allowing enumeration of attacker-controlled media before the legitimate boot partition.
  4. Check if GRUB password authentication is configured
    Inspect GRUB configuration for password hash entries: grep -r 'password_pbkdf2\|password' /boot/grub2/ or look for 'superusers' directive in grub.cfg.
    Affected if Password protection is configured. If no password is set, the bypass is not applicable since no authentication exists to bypass.
  5. Verify Secure Boot status
    Check if Secure Boot is enabled by running: mokutil --sb-state or checking /sys/firmware/efi/efivars/SecureBoot-*
    Affected if Secure Boot is disabled or not available. When disabled, unsigned or modified GRUB configurations can be loaded from alternate sources.

A system is affected if it runs in UEFI mode, uses UUID-based GRUB config location, has removable devices boot priority over internal storage, and has GRUB password protection configured while Secure Boot is disabled.

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
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Configure UEFI/BIOS to disable booting from removable devices, enforce boot order to prioritize internal storage, and enable Secure Boot with signed bootloaders to prevent unauthorized GRUB configuration loading.

Recommended fix High confidence

Red Hat Enterprise Linux 9.x: update to latest grub2 packages via 'dnf update grub2'; Fedora 38/39: update to latest grub2 packages via 'dnf update grub2'

  1. Update the system package cache: sudo dnf check-update
  2. Install the latest grub2 security updates: sudo dnf update grub2 grub2-efi-x64 grub2-common
  3. Reboot the system to ensure the updated GRUB is loaded
  4. Verify the GRUB password protection is working correctly after reboot
Caveat Updating GRUB2 may require regenerating the GRUB configuration and rebooting; ensure you have console access in case of boot issues

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

Fix this in Enterprise Linux Scoped from the published advisory
  • Consultation3.0 h
  • Implementation2.0 h
  • Testing3.0 h
  • Review / QA2.0 h
10.0 hours of engineering $1,770
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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-2023-4001 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