CVE-2021-39254

Privileged code execution via overflowed memmove length

Published Sep 7, 2021 · Updated Dec 2, 2025

Heap-based buffer overflow in Tuxera NTFS-3G before 2021.8.22 allows local users to execute privileged code via a crafted NTFS image. In ntfs_attr_record_resize, an integer overflow corrupts memmove's length calculation and turns crafted NTFS metadata into an out-of-bounds heap copy. Execution requires local access to a setuid-root ntfs-3g binary or physical insertion into a system configured to process the storage automatically.

CVSS severity7.8
High
EPSS probability0.44%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Heap-based buffer overflow in Tuxera NTFS-3G before 2021.8.22 allows local users to execute privileged code via a crafted NTFS image. In ntfs_attr_record_resize, an integer overflow corrupts memmove's length calculation and turns crafted NTFS metadata into an out-of-bounds heap copy. Execution requires local access to a setuid-root ntfs-3g binary or physical insertion into a system configured to process the storage automatically.

The record

CVE
CVE-2021-39254
Published
Sep 7, 2021
Updated
Dec 2, 2025
Vendor
Unknown vendor
Product
Unknown product
Classifications
T1068
Attack vector
local
Privileges
authenticated

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 privilegesauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

7.8CanonicalCVSS:3.1/AV:L/AC:L/PR:L/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
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

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.

Technologies

Your stack

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Your stack

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