CVE-2021-3697Known exploitation

Heap corruption via JPEG pointer underflow

Published Jul 6, 2022 · Updated Aug 3, 2024

Out-of-bounds write in The GnuPG Project GNU GRUB before 2.12 allows local users to corrupt heap data via a crafted JPEG image. The grub_jpeg_decode_data loop computes a negative bitmap stride when JPEG dimensions are narrow, underflowing the data pointer and writing outside the heap. Exploitation requires high privileges at the bootloader and careful heap-layout and payload preparation; successful corruption can cause code execution or secure-boot circumvention.

CVSS severity7.5
High
EPSS probability0.46%
Next 30 days · Sep 16, 2026
Known exploitationReported
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Out-of-bounds write in The GnuPG Project GNU GRUB before 2.12 allows local users to corrupt heap data via a crafted JPEG image. The grub_jpeg_decode_data loop computes a negative bitmap stride when JPEG dimensions are narrow, underflowing the data pointer and writing outside the heap. Exploitation requires high privileges at the bootloader and careful heap-layout and payload preparation; successful corruption can cause code execution or secure-boot circumvention.

The record

CVE
CVE-2021-3697
Published
Jul 6, 2022
Updated
Aug 3, 2024
Vendor
The GnuPG Project
Product
GNU GRUB
Classifications
CWE-787, T1068
Attack vector
local
Privileges
admin

Timeline

How it unfolded

  1. Jul 6, 2022CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

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  1. Affected versionversion=grub-2.06

What conditions does exploitation require?

Attack vectorlocal
Required privilegesadmin

What is affected?

The GnuPG Project · GNU GRUBversion=grub-2.06

Published CVSS scores

7.5GRUB security patch noticeCVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:C/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

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No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesadmin
Known exploitationReported
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-787Out-of-bounds Write
T1068Exploitation for Privilege Escalation

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Reported exploitation

Technologies

Your stack

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Your stack

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