CVE-2021-39253

Local out-of-bounds read via crafted NTFS image

Published Sep 7, 2021 · Updated Dec 2, 2025

Out-of-bounds read in ntfs_runlists_merge_i in NTFS-3G before 2021.8.22 allows attackers to read past a buffer via a crafted image. The function merges runlist metadata from the image without adequately validating a read boundary, causing an out-of-bounds access. Triggering requires local or physical access to make a configured NTFS-3G binary or utility process the image; public sources do not establish whether this individual flaw exposes data or only interrupts the process.

CVSS severity7.8
High
EPSS probability0.42%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Out-of-bounds read in ntfs_runlists_merge_i in NTFS-3G before 2021.8.22 allows attackers to read past a buffer via a crafted image. The function merges runlist metadata from the image without adequately validating a read boundary, causing an out-of-bounds access. Triggering requires local or physical access to make a configured NTFS-3G binary or utility process the image; public sources do not establish whether this individual flaw exposes data or only interrupts the process.

The record

CVE
CVE-2021-39253
Published
Sep 7, 2021
Updated
Dec 2, 2025
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-125, CWE-20, T1200
Attack vector
local
Privileges
Unavailable

Timeline

How it unfolded

  1. Sep 7, 2021CVE publishedPublication date reported by the CVE source.
  2. Dec 2, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectorlocal
Required privilegesUnavailable in this record.

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

7.8NIST NVDCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
6.7CISA-ADPCVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H
6.9NIST NVDAV:L/AC:M/Au:N/C:C/I:C/A:C

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
PrivilegesUnavailable
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-125Out-of-bounds Read
CWE-20Improper Input Validation
T1200Hardware Additions

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.

Technologies

Your stack

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Your stack

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