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Debian LinuxOperating system · Debian

CVE-2021-39257

MEDIUM · 5.5 CVSS v3.1 Published 2021-09-07
Fix available
A fix is available. Upgrade to 2021.8.22 or later.
See remediation →
57/100
Remediation priority · Elevated
Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
A crafted NTFS image with an unallocated bitmap can lead to a endless recursive function call chain (starting from ntfs_attr_pwrite), causing stack consumption in NTFS-3G < 2021.8.22.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

A crafted NTFS image containing an unallocated bitmap triggers an endless recursive function call chain originating from ntfs_attr_pwrite in NTFS-3G versions prior to 2021.8.22. This recursive loop exhausts stack memory, resulting in a denial of service condition (crash or hang) when the malicious image is mounted.

MitigationUpgrade NTFS-3G to version 2021.8.22 or later to patch the recursive call vulnerability. Avoid mounting untrusted NTFS images from unknown sources.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Debian LinuxOperating system
Affected:= 9.0= 10.0= 11.0
Ntfs 3gApplication
Affected:< 2021.8.22

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Local
Complexity
Low
Privileges
Low
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

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

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Check NTFS-3G version
    Run `ntfs-3g --version` or use package manager: `dpkg -l ntfs-3g` (Debian/Ubuntu), `rpm -q ntfs-3g` (Red Hat/CentOS), `pacman -Q ntfs-3g` (Arch).
    Affected if Version is less than 2021.8.22 (e.g., 2021.4.22, 2020.x) or package is installed but version cannot be determined (older).
  2. Verify NTFS-3G binary presence
    Run `which ntfs-3g` or list the binary: `ls -l /usr/bin/ntfs-3g /sbin/mount.ntfs`.
    Affected if The binary exists (indicates NTFS-3G is installed).
  3. Check for active NTFS mounts
    Inspect /proc/mounts for any mounts of type ntfs or ntfs-3g: `grep -E 'ntfs|fuse' /proc/mounts`.
    Affected if There are any NTFS mounts (current usage of NTFS-3G).
  4. Check for NTFS entries in /etc/fstab
    Inspect /etc/fstab for any NTFS partitions: `grep -E 'ntfs|fuse' /etc/fstab`.
    Affected if There are any NTFS entries (system configured to mount NTFS).

If NTFS-3G version is below 2021.8.22 and the system uses NTFS-3G to mount NTFS (either currently mounted or configured), the environment is affected.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 2021.8.22 or later
Fixed in 2021.8.22
Interim mitigation

Upgrade NTFS-3G to version 2021.8.22 or later to patch the recursive call vulnerability. Avoid mounting untrusted NTFS images from unknown sources.

Recommended fix High confidence

NTFS-3G version 2021.8.22 or later (Debian security updates for versions 9.0, 10.0, 11.0)

  1. Update your package repository metadata: `apt-get update`
  2. Upgrade NTFS-3G to the fixed version: `apt-get install ntfs-3g`
  3. Verify the installed version is 2021.8.22 or later: `ntfs-3g --version`
  4. If the package manager does not provide the fixed version, consider building from source available at https://github.com/tuxera/ntfs-3g/releases/tag/2021.8.22

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Debian Linux Scoped from the published advisory
  • Consultation1.0 h
  • Implementation1.0 h
  • Testing2.0 h
  • Review / QA1.0 h
5.0 hours of engineering $860
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $1,376.

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2021-39257 in production — separate from our analysis above.

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data