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Developer ToolsApplication · Redhat

CVE-2021-3697

HIGH · 7.0 CVSS v3.1 Published 2022-07-06
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
72/100
Remediation priority · Elevated
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
A crafted JPEG image may lead the JPEG reader to underflow its data pointer, allowing user-controlled data to be written in heap. To a successful to be performed the attacker needs to perform some triage over the heap layout and craft an image with a malicious format and payload. This vulnerability can lead to data corruption and eventual code execution or secure boot circumvention. This flaw affects grub2 versions prior grub-2.12.

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

A heap underflow vulnerability in GRUB2's JPEG image parser allows a crafted JPEG to write user-controlled data to heap memory through pointer underflow. Successful exploitation requires heap layout triage and a specially crafted image, potentially enabling code execution or secure boot circumvention.

MitigationUpdate GRUB2 to version 2.12 or later to patch the JPEG parser heap underflow vulnerability; re-sign the bootloader for secure boot environments.

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
Developer ToolsApplication
Affected:= 1.0
OpenshiftApplication
Affected:= 3.0
Enterprise LinuxOperating system
Affected:= 8.0= 8.1= 8.4= 9.0
Enterprise Linux EusOperating system
Affected:= 8.2= 8.4= 8.6= 9.0
Enterprise Linux For Power Little EndianOperating system
Affected:= 8.0= 9.0
Enterprise Linux For Power Little Endian EusOperating system
Affected:= 8.2= 8.4= 8.6= 9.0
Enterprise Linux Server AusOperating system
Affected:= 8.2= 8.4= 8.6
Enterprise Linux Server For Power Little Endian Update Services For Sap SolutionsOperating system
Affected:= 8.1= 8.2= 8.4= 8.6= 9.0

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

CVSS:3.1/AV:L/AC:H/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. Verify GRUB2 is installed
    Run 'grub2-install --version' or check for /boot/grub2/ or /boot/efi/EFI/*/grub*.efi
    Affected if GRUB2 is present on the system
  2. Determine GRUB2 version
    Run 'grub2-mkversion' or check the package version via 'rpm -q grub2' or 'dnf list installed grub2'
    Affected if The installed version is earlier than 2.12 and matches the affected Red Hat product versions listed in the CVE
  3. Check if JPEG support is enabled in GRUB2
    Examine GRUB configuration files in /boot/grub2/grub.cfg or /boot/efi/EFI/*/grub.cfg for the 'jpeg' module (typically loaded via 'insmod jpeg') or check for JPEG image loading in custom GRUB splash images
    Affected if The jpeg module is loaded or custom JPEG splash images are configured in GRUB menus
  4. Identify custom GRUB images
    List contents of /boot/grub2/ or /boot/efi/EFI/*/ for custom GRUB theme or background image files with .jpg or .jpeg extensions
    Affected if Custom JPEG images are present as GRUB splash/background images

A system is affected if it runs a GRUB2 version earlier than 2.12 with JPEG module support enabled and uses custom JPEG images in the GRUB configuration, as the vulnerability lies in GRUB2's JPEG parser.

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

Update GRUB2 to version 2.12 or later to patch the JPEG parser heap underflow vulnerability; re-sign the bootloader for secure boot environments.

Recommended fix High confidence

GRUB2 version 2.12 or later (grub-2.12)

  1. Update the system package cache: 'dnf check-update' or 'yum check-update'
  2. Apply the GRUB2 security update: 'dnf update grub2' or 'yum update grub2'
  3. Regenerate GRUB configuration: 'grub2-mkconfig -o /boot/grub2/grub.cfg' (for BIOS systems) or 'grub2-mkconfig -o /boot/efi/EFI/redhat/grub.cfg' (for UEFI systems)
  4. Reboot the system to load the updated GRUB2 bootloader
  5. Verify the installed GRUB2 version is 2.12 or later using: 'grub2-install --version'
Caveat Updating GRUB2 requires regenerating the GRUB config and rebooting; ensure any custom GRUB modifications are backed up before applying the update

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

Fix this in Developer Tools Scoped from the published advisory
  • Consultation6.0 h
  • Implementation12.0 h
  • Testing8.0 h
  • Review / QA4.0 h
30.0 hours of engineering $5,280
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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-2021-3697 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