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CVE-2026-64388

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

HIGH
7.8
CVSS Score
Published: July 25, 2026 at 08:50 AM UTC
Updated: October 21, 2026 at 01:19 PM UTC
1 product affected across 1 vendorLinux Kernel

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Severity
HIGH7.8
Exploit prediction
EPSS 0.1%
SSVC
No known exploit

Description

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

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

Linux Kernel· Linux
95%
4.18 ≤ v < 7.1.44.18b326614ea2159ea5c835d320f261d05d080cd201
Vendor states this is fixed in 550cfb8a81181331d4d0f76ab75ee58a0bf41e3e (fixed)
Vendor states this is fixed in 760ef2c579c2609cf17fb1cd5392f64d42d43d33 (fixed)
Vendor states this is fixed in 4.18 (unaffected)
Vendor states this is fixed in 6.12.114 (unaffected)
Vendor states this is fixed in 6.18.57 (unaffected)
Vendor states this is fixed in 6.6.160 (unaffected)
Vendor states this is fixed in 7.1.4 (unaffected)
Vendor states this is fixed in 7.2 (unaffected)

Remediation

No guide yet

No remediation guidance has been written for this CVE yet. What the record does show:

Patch and advisory references

References (5)

Patch
Source: cverecord
https://git.kernel.org/stable/c/550cfb8a81181331d4d0f76ab75ee58a0bf41e3e
Patch
Source: cverecord
https://git.kernel.org/stable/c/760ef2c579c2609cf17fb1cd5392f64d42d43d33
Source: cverecord
https://git.kernel.org/stable/c/3eaec47518e126e6dcd1a48521d740278073f0ec
Source: cverecord
https://git.kernel.org/stable/c/6825a45f6b8ef76b0ee32649ec3d6e39ca143a18
Source: cverecord
https://git.kernel.org/stable/c/27ead8c5418af6bfab711079fecb9414d78d4cae

SSVC — Action Prioritization

SSVCNo known exploitNot automatableTotal impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

7.8HIGHLinux
Vector?

Quick Info

StatusMODIFIED
CWE
NVD-CWE-noinfoCWE-682

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