What is CVE-2026-64388?

CVE-2026-64388 is a High severity Linux kernel vulnerability with a CVSS score of 7.8 out of 10, classified as a Incorrect Calculation flaw (CWE-682), affecting Linux kernel versions from 4.18 onward and patched in 6.6.160, 6.12.114, 6.18.57 and others. CVE-2026-64388 has not been confirmed as actively exploited and is not listed in the CISA KEV catalog.

What is the CVSS score for CVE-2026-64388?

CVE-2026-64388 has a CVSS score of 7.8 out of 10, rated High severity. The vector string is CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H.

Is there a patch available for CVE-2026-64388?

Yes, CVE-2026-64388 has been patched. Fixed versions include 6.6.160, 6.12.114, 6.18.57 and others. If you are running Linux kernel 4.18 or later up to the fix versions, apply the relevant patch for your kernel branch.

Is CVE-2026-64388 actively exploited?

CVE-2026-64388 has not been confirmed as actively exploited and is not listed in the CISA KEV catalog.

What is Incorrect Calculation (CWE-682)?

The product performs a calculation that generates incorrect or unintended results. See MITRE CWE for full details: https://cwe.mitre.org/data/definitions/682.html

CVE-2026-64388

High

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.

Package Linux Kernel

Published 2026-07-25

Last modified 2026-10-19

CVSS version 3.1

Patch available

Yes

CVSS 3.1 score

7.8

out of 10

High

Attack Vector

Local

Attack Complexity

Low

Privileges Required

Low

User Interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

High

Availability

High

Vector string

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Weakness type

CWE-682

CVE-2026-64388 is a Incorrect Calculation vulnerability

What is Incorrect Calculation?

The product performs a calculation that generates incorrect or unintended results. Learn more on MITRE CWE

Affected versions

Linux kernel versions 4.18 and later are affected. Fixed in 6.6.160, 6.12.114, 6.18.57, 7.1.4, 7.2 and their respective stable series.

Affected from

≥ 4.18

Fixed in

✓ 6.6.160 6.6.x ✓ 6.12.114 6.12.x ✓ 6.18.57 6.18.x ✓ 7.1.4 7.1.x ✓ 7.2

References

3 total

Kernel Git
https://git.kernel.org/stable/c/550cfb8a81181331d4d0f76ab75ee58a0bf41e3e

Patch
Kernel Git
https://git.kernel.org/stable/c/760ef2c579c2609cf17fb1cd5392f64d42d43d33

Patch
Kernel Git
https://git.kernel.org/stable/c/3eaec47518e126e6dcd1a48521d740278073f0ec

Details

CVE ID CVE-2026-64388

Severity High

CVSS score 7.8 / 10

CVSS version 3.1

Published 2026-07-25

Modified 2026-10-19

KEV No

Patch

Yes

Package linux

Frequently asked questions

What is CVE-2026-64388?

CVE-2026-64388 is a High severity Linux kernel vulnerability with a CVSS score of 7.8 out of 10 , classified as an Incorrect Calculation flaw (CWE-682) . It affects Linux kernel versions from 4.18 onward and has been patched in 6.6.160, 6.12.114, 6.18.57 and others. CVE-2026-64388 has not been confirmed as actively exploited and is not listed in the CISA KEV catalog.
What is the CVSS score for CVE-2026-64388?

CVE-2026-64388 has a CVSS score of 7.8 out of 10, rated High severity (CVSS 3.1). The vector string is CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H.
Is there a patch available for CVE-2026-64388?

Yes. CVE-2026-64388 has been patched. Fixed versions include 6.6.160, 6.12.114, 6.18.57 and others. If you are running Linux kernel 4.18 or later up to the fix versions, apply the relevant patch for your kernel branch.
Is CVE-2026-64388 actively exploited?

No. CVE-2026-64388 has not been confirmed as actively exploited. It is not listed in the CISA Known Exploited Vulnerabilities (KEV) catalog.