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Fencer Vulns
high 7.8

CVE-2026-64388 json

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

published 2026-07-25 3 mo ago modified 2026-10-30 9 d ago also EUVD-2026-48932

cvss
7.8
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.1%
EPSS 0.1% chance of exploitation in 30 days, percentile 2%
public exploits
0
none known

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 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.

Patch / fix

  • Linux Linux 6.1.191, 6.6.160, 6.12.114, 6.18.57, 7.1.4, 7.2
  • linux Debian 13 6.12.115-2
  • linux Debian 14 7.1.4-1

debian advisories DEBIAN-CVE-2026-64388

  • linux Ubuntu 26.04 LTS 7.0.0-31.31
  • linux-aws Ubuntu 26.04 LTS 7.0.0-1012.12
  • linux-gcp Ubuntu 26.04 LTS 7.0.0-1011.11
  • linux-gke Ubuntu 26.04 LTS 7.0.0-1006.7
  • linux-ibm Ubuntu 26.04 LTS 7.0.0-1013.13
  • linux-azure Ubuntu 26.04 LTS 7.0.0-1014.14
  • linux-raspi Ubuntu 26.04 LTS 7.0.0-1019.19
  • linux-riscv Ubuntu 26.04 LTS 7.0.0-31.31.1

ubuntu advisories UBUNTU-CVE-2026-64388

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • kernel-default SLES 16.0, SLE High Availability Extension 16.0, Linux Micro 6.2 +1 more 6.12.0-160000.39.1
  • kernel-rt Linux Micro 6.2 6.12.0-160000.39.1
  • kernel-64kb SLES 16.0, Linux Micro 6.2, SLES for SAP applications 16.0 6.12.0-160000.39.1
  • kernel-source SLES 16.0, Linux Micro 6.2, SLES for SAP applications 16.0 6.12.0-160000.39.1
  • kernel-default-base SLES 16.0, Linux Micro 6.2, SLES for SAP applications 16.0 6.12.0-160000.39.1.160000.2.26
  • kernel-syms SLES 16.0, Linux Micro Extras 6.2, SLES for SAP applications 16.0 6.12.0-160000.39.1
  • kernel-azure SLES for SAP applications 16.0, SLES 16.0 6.12.0-160000.39.1
  • kernel-obs-qa SLES for SAP applications 16.0, SLES 16.0 6.12.0-160000.39.1

suse advisories SUSE-SU-2026:4687-1SUSE-SU-2026:24197-1SUSE-SU-2026:24184-1SUSE-SU-2026:24235-1SUSE-SU-2026:24179-1SUSE-SU-2026:4254-1

  • kernel-rt openSUSE Leap 16.0 6.12.0-160000.39.1
  • dtb-aarch64 openSUSE Leap 16.0 6.12.0-160000.39.1
  • kernel-64kb openSUSE Leap 16.0 6.12.0-160000.39.1
  • kernel-syms openSUSE Leap 16.0 6.12.0-160000.39.1
  • kernel-azure openSUSE Leap 16.0 6.12.0-160000.39.1
  • kernel-obs-qa openSUSE Leap 16.0 6.12.0-160000.39.1
  • kernel-source openSUSE Leap 16.0 6.12.0-160000.39.1
  • kernel-default openSUSE Leap 16.0 6.12.0-160000.39.1

opensuse advisories openSUSE-SU-2026:22091-1openSUSE-SU-2026:11476-1

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-64388 updated cvss 5.5

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

  • Red Hat Enterprise Linux 8 perf, kernel, bpftool, kernel-rt, kernel-core, kernel-tools, +29 more Red Hat Enterprise Linux 9 rv, perf, rtla, kernel, bpftool, libperf, +83 more Red Hat Enterprise Linux 10 kernel
    affected: no fix available “Fix deferred”
  • Red Hat Enterprise Linux 6 perf, kernel, python-perf, kernel-kdump, kernel-firmware, kernel-bootwrapper, +1 more Red Hat Enterprise Linux 7 perf, kernel, bpftool, kernel-rt, python-perf, kernel-kdump, +8 more
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
total
Assessed
23 d ago

Exploit prediction

0.13% chance of exploitation in the next 30 days, higher than 2% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 7.8 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Affected products

  • Linux Linux

Classification

Weakness
Technology feeds

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.