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NVD / CVE Program· CNA redhat

CVE-2021-3695: A crafted 16-bit grayscale PNG image may lead to a out-of-bounds write in the heap area.

Noroxi assessment

Priority: Monitor (action score 18/100)

  • The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
  • Probability of exploitation in the next 30 days: 0.46% (FIRST EPSS).
  • Someone with local access to the system can trigger it. A low-privileged account is enough. No user action is required. Special conditions such as timing or configuration are required.
  • Fixed version: grub2-common (AlmaLinux:8) 1:2.02-123.el8_6.8.alma; grub2-efi-aa64 (AlmaLinux:8) 1:2.02-123.el8_6.8.alma; grub2-efi-aa64-cdboot (AlmaLinux:8) 1:2.02-123.el8_6.8.alma.
  • Mentioned 1 time in Turkish national cyber security advisories (siberguvenlik.gov.tr).

Low priority for now. Upgrade to grub2-common (AlmaLinux:8) 1:2.02-123.el8_6.8.alma; grub2-efi-aa64 (AlmaLinux:8) 1:2.02-123.el8_6.8.alma; grub2-efi-aa64-cdboot (AlmaLinux:8) 1:2.02-123.el8_6.8.alma or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

A crafted 16-bit grayscale PNG image may lead to a out-of-bounds write in the heap area. An attacker may take advantage of that to cause heap data corruption or eventually arbitrary code execution and circumvent secure boot protections. This issue has a high complexity to be exploited as an attacker needs to perform some triage over the heap layout to achieve signifcant results, also the values written into the memory are repeated three times in a row making difficult to produce valid payloads. This flaw affects grub2 versions prior grub-2.12.

MediumCVSS 4.5 · v3.1—No exploit Fix available
Published
Jul 6, 2022
Updated
Jun 17, 2026
EPSS
0.4% · 40th percentile

Report tools

JSON

Action score

18

Monitor

Low priority for now.

CVSS
18 / 40 · 4.5 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.4%

Get told when this record changes

  • Not in KEV: no record of exploitation in the wild
  • No public exploit code on record
  • A fix has been released

If any of these changes, we'll tell you in the daily email digest.

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  • when exploit code appears or is weaponized
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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

VendorProduct
gnugrub2
fedoraprojectfedora
redhatdeveloper tools
redhatopenshift
redhatenterprise linux
redhatenterprise linux eus
redhatenterprise linux for power little endian
redhatenterprise linux for power little endian eus
redhatenterprise linux server aus
redhatenterprise linux server for power little endian update services for sap solutions
redhatenterprise linux server tus
redhatopenshift container platform

and 2 more

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • fedoraproject fedora36
  • gnu grub22.00 and later · before 2.12
  • netapp ontap select deploy administration utilityall versions
  • redhat codeready linux builderall versions
  • redhat developer tools1.0
  • redhat enterprise linux8.0
  • redhat enterprise linux8.1
  • redhat enterprise linux8.4
  • redhat enterprise linux9.0
  • redhat enterprise linux eus8.2
  • redhat enterprise linux eus8.4
  • redhat enterprise linux eus8.6
  • redhat enterprise linux eus9.0
  • redhat enterprise linux for power little endian8.0
  • redhat enterprise linux for power little endian9.0
  • redhat enterprise linux for power little endian eus8.2
  • redhat enterprise linux for power little endian eus8.4
  • redhat enterprise linux for power little endian eus8.6
  • redhat enterprise linux for power little endian eus9.0
  • redhat enterprise linux server aus8.2

Versions reported by the vendor

Affected version ranges reported by the assigning authority (redhat). Independent of NVD's CPE analysis and usually ahead of it.

  • n/a grub2

    • grub-2.06affected

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
AlmaLinux:8grub2-commonbefore 1:2.02-123.el8_6.8.alma1:2.02-123.el8_6.8.alma
AlmaLinux:8grub2-efi-aa64before 1:2.02-123.el8_6.8.alma1:2.02-123.el8_6.8.alma
AlmaLinux:8grub2-efi-aa64-cdbootbefore 1:2.02-123.el8_6.8.alma1:2.02-123.el8_6.8.alma
AlmaLinux:8grub2-efi-aa64-modulesbefore 1:2.02-123.el8_6.8.alma1:2.02-123.el8_6.8.alma
AlmaLinux:8grub2-efi-ia32before 1:2.02-123.el8_6.8.alma1:2.02-123.el8_6.8.alma
AlmaLinux:8grub2-efi-ia32-cdbootbefore 1:2.02-123.el8_6.8.alma1:2.02-123.el8_6.8.alma
AlmaLinux:8grub2-efi-ia32-modulesbefore 1:2.02-123.el8_6.8.alma1:2.02-123.el8_6.8.alma
AlmaLinux:8grub2-efi-x64before 1:2.02-123.el8_6.8.alma1:2.02-123.el8_6.8.alma
AlmaLinux:8grub2-efi-x64-cdbootbefore 1:2.02-123.el8_6.8.alma1:2.02-123.el8_6.8.alma
AlmaLinux:8grub2-efi-x64-modulesbefore 1:2.02-123.el8_6.8.alma1:2.02-123.el8_6.8.alma
AlmaLinux:8grub2-pcbefore 1:2.02-123.el8_6.8.alma1:2.02-123.el8_6.8.alma
AlmaLinux:8grub2-pc-modulesbefore 1:2.02-123.el8_6.8.alma1:2.02-123.el8_6.8.alma
AlmaLinux:8grub2-ppc64le-modulesbefore 1:2.02-123.el8_6.8.alma1:2.02-123.el8_6.8.alma
AlmaLinux:8grub2-toolsbefore 1:2.02-123.el8_6.8.alma1:2.02-123.el8_6.8.alma
AlmaLinux:8grub2-tools-efibefore 1:2.02-123.el8_6.8.alma1:2.02-123.el8_6.8.alma
AlmaLinux:8grub2-tools-extrabefore 1:2.02-123.el8_6.8.alma1:2.02-123.el8_6.8.alma
AlmaLinux:8grub2-tools-minimalbefore 1:2.02-123.el8_6.8.alma1:2.02-123.el8_6.8.alma
AlmaLinux:8shim-aa64before 15.6-1.el8.alma15.6-1.el8.alma
AlmaLinux:8shim-ia32before 15.6-1.el8.alma15.6-1.el8.alma
AlmaLinux:8shim-unsigned-x64before 15.6-1.el8.alma15.6-1.el8.alma
AlmaLinux:8shim-x64before 15.6-1.el8.alma15.6-1.el8.alma
AlmaLinux:9grub2-commonbefore 1:2.06-27.el9_0.7.alma1:2.06-27.el9_0.7.alma
AlmaLinux:9grub2-efi-aa64before 1:2.06-27.el9_0.7.alma1:2.06-27.el9_0.7.alma
AlmaLinux:9grub2-efi-aa64-cdbootbefore 1:2.06-27.el9_0.7.alma1:2.06-27.el9_0.7.alma

+96

Same product

gnu: all records

Other highest-scoring records for the same primary product.

  • CVE-2024-56737GNU GRUB (aka GRUB2) through 2.12 has a heap-based buffer overflow in fs/hfs.c via crafted sblock data in an HFS filesystem.
    35Monitor
  • CVE-2022-2601A buffer overflow was found in grub_font_construct_glyph().
    34Monitor
  • CVE-2020-10713A flaw was found in grub2, prior to version 2.06.
    33Monitor

Published before and after this one in the same product

  • ← EarlierCVE-2021-3418Mar 15, 2021 · If certificates that signed grub are installed into db, grub can be booted directly.
    25Monitor
  • ← EarlierCVE-2021-3981Mar 10, 2022 · A flaw in grub2 was found where its configuration file, known as grub.cfg, is being created with the wrong permission set allowing non privi
    13Monitor
  • Later →CVE-2021-3696Jul 6, 2022 · A heap out-of-bounds write may heppen during the handling of Huffman tables in the PNG reader.
    18Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
almalinux:grub2-common1:2.02-123.el8_6.8.alma · AlmaLinux:8Package registry (OSV)
almalinux:grub2-efi-aa641:2.02-123.el8_6.8.alma · AlmaLinux:8Package registry (OSV)
almalinux:grub2-efi-aa64-cdboot1:2.02-123.el8_6.8.alma · AlmaLinux:8Package registry (OSV)
almalinux:grub2-efi-aa64-modules1:2.02-123.el8_6.8.alma · AlmaLinux:8Package registry (OSV)
almalinux:grub2-efi-ia321:2.02-123.el8_6.8.alma · AlmaLinux:8Package registry (OSV)
almalinux:grub2-efi-ia32-cdboot1:2.02-123.el8_6.8.alma · AlmaLinux:8Package registry (OSV)
almalinux:grub2-efi-ia32-modules1:2.02-123.el8_6.8.alma · AlmaLinux:8Package registry (OSV)
almalinux:grub2-efi-x641:2.02-123.el8_6.8.alma · AlmaLinux:8Package registry (OSV)
almalinux:grub2-efi-x64-cdboot1:2.02-123.el8_6.8.alma · AlmaLinux:8Package registry (OSV)
almalinux:grub2-efi-x64-modules1:2.02-123.el8_6.8.alma · AlmaLinux:8Package registry (OSV)
almalinux:grub2-pc1:2.02-123.el8_6.8.alma · AlmaLinux:8Package registry (OSV)
almalinux:grub2-pc-modules1:2.02-123.el8_6.8.alma · AlmaLinux:8Package registry (OSV)
debian:grub22.06-3 · Debian:12Package registry (OSV)
opensuse:grub22.06-150400.11.5.2 · openSUSE:Leap 15.4Package registry (OSV)
red hat:grub21:2.02-123.el8_6.8 · Red Hat:enterprise_linux:8::baseosPackage registry (OSV)
red hat:grub2-common1:2.02-123.el8_6.8 · Red Hat:enterprise_linux:8::baseosPackage registry (OSV)
red hat:grub2-debuginfo1:2.02-123.el8_6.8 · Red Hat:enterprise_linux:8::baseosPackage registry (OSV)
red hat:grub2-debugsource1:2.02-123.el8_6.8 · Red Hat:enterprise_linux:8::baseosPackage registry (OSV)
red hat:grub2-efi-aa641:2.02-123.el8_6.8 · Red Hat:enterprise_linux:8::baseosPackage registry (OSV)
red hat:grub2-efi-aa64-cdboot1:2.02-123.el8_6.8 · Red Hat:enterprise_linux:8::baseosPackage registry (OSV)
red hat:grub2-efi-aa64-modules1:2.02-123.el8_6.8 · Red Hat:enterprise_linux:8::baseosPackage registry (OSV)
red hat:grub2-efi-ia321:2.02-123.el8_6.8 · Red Hat:enterprise_linux:8::baseosPackage registry (OSV)
red hat:grub2-efi-ia32-cdboot1:2.02-123.el8_6.8 · Red Hat:enterprise_linux:8::baseosPackage registry (OSV)
red hat:grub2-efi-ia32-modules1:2.02-123.el8_6.8 · Red Hat:enterprise_linux:8::baseosPackage registry (OSV)
red hat:grub2-efi-x641:2.02-123.el8_6.8 · Red Hat:enterprise_linux:8::baseosPackage registry (OSV)
red hat:grub2-efi-x64-cdboot1:2.02-123.el8_6.8 · Red Hat:enterprise_linux:8::baseosPackage registry (OSV)
rocky linux:grub21:2.02-123.el8_6.8 · Rocky Linux:8Package registry (OSV)
rocky linux:mokutil1:0.3.0-11.el8_6.1 · Rocky Linux:8Package registry (OSV)
rocky linux:shim0:15.6-1.el8 · Rocky Linux:8Package registry (OSV)
rocky linux:shim-unsigned-x640:15.6-1.el8 · Rocky Linux:8Package registry (OSV)

+1

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

No history yet (it accumulates with the daily EPSS job).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

No nightly-computed relations.

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

National notice (Türkiye Cybersecurity Directorate / USOM)

Official security notices citing this record; remediation advice is on the agency's page.

All national notices →

Technical details

Attack conditions

  • Someone with local access to the system can trigger it.
  • A low-privileged account is enough.
  • No user action is required.
  • Special conditions such as timing or configuration are required.

If successful

Confidentiality
low · data can be read
Integrity
low · data or configuration can be modified
Availability
low · the service can be disrupted
Attack vector
Local
Attack complexity
High
Privileges required
Low
User interaction
None
Scope
Unchanged
Confidentiality impact
Low
Integrity impact
Low
Availability impact
Low

Weakness class (CWE)

CWE-787 · Out-of-bounds Write

CVSS vector

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

nvd-primary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

MITRE has no CAPEC/ATT&CK mapping for this CWE.

Change log

  1. Fix✗ → ✓

For records you follow, these changes also arrive as notifications. →

References

Show all references (2 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records