CVE-2021-39257

Local crash via recursive attribute writes

Published Sep 7, 2021 · Updated Aug 4, 2024

Uncontrolled recursion in NTFS-3G before 2021.8.22 allows local users to crash NTFS-3G with a crafted NTFS image. An unallocated bitmap causes ntfs_attr_pwrite to enter an endless recursive call chain that consumes the process stack. Exploitation requires local access to process or mount the image and causes an availability-only service interruption.

CVSS severity5.5
Medium
EPSS probability0.40%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Uncontrolled recursion in NTFS-3G before 2021.8.22 allows local users to crash NTFS-3G with a crafted NTFS image. An unallocated bitmap causes ntfs_attr_pwrite to enter an endless recursive call chain that consumes the process stack. Exploitation requires local access to process or mount the image and causes an availability-only service interruption.

The record

CVE
CVE-2021-39257
Published
Sep 7, 2021
Updated
Aug 4, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-674, CAPEC-230, CAPEC-231, T1499.004
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Sep 7, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 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?

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

4.7NIST NVDAV:L/AC:M/Au:N/C:N/I:N/A:C
5.5NIST NVDCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/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

CWE-674Uncontrolled Recursion
CAPEC-230Serialized Data with Nested Payloads
CAPEC-231Oversized Serialized Data Payloads
T1499.004Application or System Exploitation

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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