dbcve.org
Grub2Application · Gnu

CVE-2022-28733

HIGH · 8.1 CVSS v3.1 Published 2023-07-20
Fix available
A fix is available. Upgrade to 2.06-3 or later.
See remediation →
90/100
Remediation priority · Urgent
Remotely reachable 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
Integer underflow in grub_net_recv_ip4_packets; A malicious crafted IP packet can lead to an integer underflow in grub_net_recv_ip4_packets() function on rsm->total_len value. Under certain circumstances the total_len value may end up wrapping around to a small integer number which will be used in memory allocation. If the attack succeeds in such way, subsequent operations can write past the end of the buffer.

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

Integer underflow in GRUB's grub_net_recv_ip4_packets() function allows a maliciously crafted IP packet to cause the rsm->total_len value to wrap around to a small number. This undersized value is then used for memory allocation, causing subsequent buffer operations to write past the allocated buffer boundary, leading to potential code execution.

MitigationApply the GRUB security patch that adds proper validation of the total_len value before memory allocation to prevent integer underflow. Update GRUB to the latest patched version on affected systems.

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
Network
Complexity
High
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:H/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. Identify if GRUB2 is the installed bootloader
    Check for GRUB2 files in /boot/grub2, /boot/efi/EFI, or look for grub2-install on the system. On Linux, examine /boot/grub2/grub.cfg or check the EFI bootloader files.
    Affected if GRUB2 is present as the system bootloader
  2. Determine the installed GRUB2 version
    Run `grub2-install --version` or `grub-mkversion` if available. On RPM-based systems, check the package version with `rpm -q grub2` or `rpm -q grub2-efi-x64`. On Debian-based systems, check with `dpkg -l | grep grub` or examine the bootloader file directly.
    Affected if The version is >= 2.00 and < 2.06-3
  3. Check if network/PXE boot is configured
    Examine the GRUB configuration file (/boot/grub2/grub.cfg or /boot/grub/grub.cfg) for network boot menu entries. Look for lines containing 'net_bootp', 'pxe', or 'tftp'. Also check if the system has a PXE boot infrastructure.
    Affected if Network boot or PXE boot functionality is enabled in GRUB configuration
  4. Verify the network packet receiving code is in use
    This vulnerability is triggered when GRUB receives IPv4 packets during network boot. Check if the system boots from network/PXE or uses iSCSI with network transport. Review any custom GRUB modules loaded for network support in /boot/grub2/i386-pc or /boot/grub2/x86_64-efi.
    Affected if The system uses GRUB network boot features to load from network resources

The system is affected if GRUB2 version is >= 2.00 and < 2.06-3 AND the system uses GRUB network boot or PXE boot functionality.

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

Apply the GRUB security patch that adds proper validation of the total_len value before memory allocation to prevent integer underflow. Update GRUB to the latest patched version on affected systems.

Recommended fix High confidence

Grub2 2.06-3 or later

  1. Obtain Grub2 version 2.06-3 or later from official GNU GRUB distribution channels or your Linux distribution's package repositories
  2. Verify the package integrity using published checksums or signatures
  3. Back up the current GRUB2 installation and configuration files
  4. Install/upgrade the GRUB2 package through your distribution's package manager or by rebuilding from source
  5. Regenerate GRUB configuration files (e.g., running grub-mkconfig or update-grub)
  6. Update the MBR/EFI boot sector if necessary (e.g., grub-install /dev/sda or efibootmgr)
  7. Reboot the system and verify the new GRUB2 version loads correctly
Caveat GRUB2 upgrades require careful testing in a non-production environment first; bootloader changes can prevent system boot if misconfigured

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

Fix this in Grub2 Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing8.0 h
  • Review / QA4.0 h
24.0 hours of engineering $4,160
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $6,656.

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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-2022-28733 in production — separate from our analysis above.

No notes yet

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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