CVE-2021-39251

Local crash via crafted NTFS image

Published Sep 7, 2021 · Updated Dec 2, 2025

NULL pointer dereference in NTFS-3G before 2021.8.22 allows local users to crash the driver with a crafted NTFS image. ntfs_extent_inode_open dereferences a null pointer while opening extent-inode metadata from the attacker-controlled filesystem image. Triggering it requires the crafted image to be processed by the driver; the bounded documented outcome for this CVE is a process crash.

CVSS severity6.7
Medium
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

NULL pointer dereference in NTFS-3G before 2021.8.22 allows local users to crash the driver with a crafted NTFS image. ntfs_extent_inode_open dereferences a null pointer while opening extent-inode metadata from the attacker-controlled filesystem image. Triggering it requires the crafted image to be processed by the driver; the bounded documented outcome for this CVE is a process crash.

The record

CVE
CVE-2021-39251
Published
Sep 7, 2021
Updated
Dec 2, 2025
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-20, CWE-476, T1200
Attack vector
local
Privileges
admin

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 privilegesadmin

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

6.7CISA-ADPCVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H

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.

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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
Privilegesadmin
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-20Improper Input Validation
CWE-476NULL Pointer Dereference
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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