---
id: CVE-2026-64399
title: |-
  In the Linux kernel, the following vulnerability has been resolved:

  ksmbd: add permission checks for FSCTL_DUPLICATE_EXTENTS_TO_FILE

  The FSCTL_DUPLICATE_EXTENTS_TO_FILE arm of smb2_ioctl() overwrites the
  destination file's data via vfs…
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  ksmbd: add permission checks for FSCTL_DUPLICATE_EXTENTS_TO_FILE

  The FSCTL_DUPLICATE_EXTENTS_TO_FILE arm of smb2_ioctl() overwrites the
  destination file's data via vfs…
severity: critical
cvss: 9.8
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H'
vendor: linux
product: linux_kernel
affected:
  - 'linux_kernel >= 5.15, < 6.1.178'
  - 'linux_kernel >= 6.2, < 6.6.145'
  - 'linux_kernel >= 6.7, < 6.12.96'
  - 'linux_kernel >= 6.13, < 6.18.39'
  - 'linux_kernel >= 6.19, < 7.1.4'
patched:
  - linux_kernel 7.1.4
published: '2026-07-25'
updated: '2026-09-04'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-64399'
references:
  - url: 'https://git.kernel.org/stable/c/388e4139db27a9e3612c9d356b826f5b1ff6a9e3'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/620d133d469295ee7c017ca6aafac335f65c4a5a'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/9b9cf7e65cbeaae1b6636144bacee611cdd7a5d6'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/baae7b39673ec21073a25e3d14f8feaada01d5df'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/bf460ad5958d506492de4524a656439da3f99c51'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/c917e4522d251071dde9871b9142d8ea1186ebfe'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
tags:
  - nvd
epss: 0.00721
epssPercentile: 0.51958
ingestedAt: '2026-09-05T13:39:57.817Z'
---

## Overview

In the Linux kernel, the following vulnerability has been resolved:

ksmbd: add permission checks for FSCTL_DUPLICATE_EXTENTS_TO_FILE

The FSCTL_DUPLICATE_EXTENTS_TO_FILE arm of smb2_ioctl() overwrites the
destination file's data via vfs_clone_file_range() with neither the
share-level KSMBD_TREE_CONN_FLAG_WRITABLE check nor a per-handle
fp->daccess check that the other write-bearing arms carry. A client can
overwrite destination data on a read-only share, or from a handle opened
with only FILE_WRITE_ATTRIBUTES (which still yields an FMODE_WRITE filp).
FILE_WRITE_ATTRIBUTES-only destination handle overwrote the file's data via
the clone. Add both checks, matching the FSCTL_SET_SPARSE permission fix;
require FILE_WRITE_DATA since this writes data.

## Affected

- `linux_kernel >= 5.15, < 6.1.178`
- `linux_kernel >= 6.2, < 6.6.145`
- `linux_kernel >= 6.7, < 6.12.96`
- `linux_kernel >= 6.13, < 6.18.39`
- `linux_kernel >= 6.19, < 7.1.4`

## Remediation

Upgrade past the affected range:

- `linux_kernel 7.1.4`