---
id: CVE-2026-64388
title: |-
  In the Linux kernel, the following vulnerability has been resolved:

  smb/client: fix chown/chgrp with SMB3 POSIX Extensions

  Ownership (chown) and group (chgrp) modifications were being ignored when
  mounting with SMB3 POSIX Extensions un…
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  smb/client: fix chown/chgrp with SMB3 POSIX Extensions

  Ownership (chown) and group (chgrp) modifications were being ignored when
  mounting with SMB3 POSIX Extensions un…
severity: high
cvss: 7.8
cvssVector: 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H'
vendor: linux
product: linux_kernel
affected:
  - 'linux_kernel >= 4.18, < 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-2026-64388'
references:
  - url: 'https://git.kernel.org/stable/c/550cfb8a81181331d4d0f76ab75ee58a0bf41e3e'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/760ef2c579c2609cf17fb1cd5392f64d42d43d33'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
tags:
  - nvd
epss: 0.0012
epssPercentile: 0.0213
ingestedAt: '2026-09-05T13:39:57.352Z'
---

## Overview

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

smb/client: fix chown/chgrp with SMB3 POSIX Extensions

Ownership (chown) and group (chgrp) modifications were being ignored when
mounting with SMB3 POSIX Extensions unless CIFS_MOUNT_CIFS_ACL or
CIFS_MOUNT_MODE_FROM_SID were also explicitly set.

Fix this by checking for posix_extensions in cifs_setattr_nounix() when
updating UID and GID, ensuring that id_mode_to_cifs_acl() is called to map
and set the ownership/group information on the server.

## Affected

- `linux_kernel >= 4.18, < 7.1.4`

## Remediation

Upgrade past the affected range:

- `linux_kernel 7.1.4`