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Heap-based Buffer OverflowWeakness · CWE-122

CVE-2026-40706

HIGH · 8.4 CVSS v3.1 Published 2026-04-21
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
89/100
Remediation priority · High
No privileges 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
In NTFS-3G 2022.10.3 before 2026.2.25, a heap buffer overflow exists in ntfs_build_permissions_posix() in acls.c that allows an attacker to corrupt heap memory in the SUID-root ntfs-3g binary by crafting a malicious NTFS image. The overflow is triggered on the READ path (stat, readdir, open) when processing a security descriptor with multiple ACCESS_DENIED ACEs containing WRITE_OWNER from distinct group SIDs.

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 · moderate confidence

Heap buffer overflow in ntfs_build_permissions_posix() in acls.c allows corruption of heap memory when the SUID-root ntfs-3g binary processes a malicious NTFS image containing a security descriptor with multiple ACCESS_DENIED ACEs that have WRITE_OWNER permission from distinct group SIDs. The overflow is triggered on READ operations (stat, readdir, open).

MitigationUpgrade NTFS-3G to version 2026.2.25 or later. Avoid mounting untrusted or unknown NTFS images until the update is applied, as the vulnerability is triggerable through normal file access operations.

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

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
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/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. Identify ntfs-3g installation and version
    Run 'ntfs-3g --version' or check your system's package manager for the ntfs-3g package version
    Affected if The installed version is earlier than 2026.2.25
  2. Verify ntfs-3g binary permissions
    Run 'ls -la /bin/ntfs-3g' or 'ls -la /sbin/mount.ntfs' to check if the binary has SUID-root permissions (look for 's' in the owner execute field)
    Affected if The ntfs-3g binary has SUID-root permissions (setuid bit) and the version is below 2026.2.25
  3. Determine if ntfs-3g handles NTFS mounts
    Check /etc/fstab for entries using ntfs-3g, or run 'mount | grep ntfs' to see if any NTFS filesystems are currently mounted via ntfs-3g
    Affected if ntfs-3g is configured to mount NTFS filesystems on the system
  4. Check for untrusted NTFS image access
    Review whether users can mount NTFS images (via loop devices) or attach external NTFS storage from untrusted sources
    Affected if Untrusted or unknown NTFS images can be mounted using ntfs-3g on the system

You are affected if ntfs-3g with SUID-root permissions and version below 2026.2.25 is used to mount NTFS filesystems, including potentially untrusted NTFS images.

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
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Upgrade NTFS-3G to version 2026.2.25 or later. Avoid mounting untrusted or unknown NTFS images until the update is applied, as the vulnerability is triggerable through normal file access operations.

Recommended fix Moderate confidence

NTFS-3G version 2026.2.25 or later

  1. Identify the currently installed NTFS-3G version using 'ntfs-3g --version' or your package manager
  2. Download NTFS-3G version 2026.2.25 or later from the official source (https://github.com/tuxera/ntfs-3g)
  3. Verify the GPG signature of the downloaded package if available
  4. Upgrade NTFS-3G using your distribution's package manager or compile from source
  5. Verify the new version is installed correctly
  6. If using ntfs-3g as an SUID binary, verify permissions are correctly set after upgrade (should be -rwsr-xr-x root:root)
  7. Test NTFS mount functionality to ensure the upgrade did not break existing configurations
Caveat Standard upgrade risk - test NTFS mount configurations after upgrading, particularly any custom ACL or permission settings

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

Have this fixed Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing6.0 h
  • Review / QA4.0 h
22.0 hours of engineering $3,860
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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-2026-40706 in production — separate from our analysis above.

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What this is

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What belongs here
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  • Version or environment caveats, and links to real fixes
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