What is CVE-2026-64399?

CVE-2026-64399 is a Critical severity Linux kernel vulnerability with a CVSS score of 9.8 out of 10, affecting Linux kernel versions from 5.15 onward and patched in 6.1.178, 6.6.145, 6.12.96 and others. CVE-2026-64399 has not been confirmed as actively exploited and is not listed in the CISA KEV catalog.

What is the CVSS score for CVE-2026-64399?

CVE-2026-64399 has a CVSS score of 9.8 out of 10, rated Critical severity. The vector string is CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.

Is there a patch available for CVE-2026-64399?

Yes, CVE-2026-64399 has been patched. Fixed versions include 6.1.178, 6.6.145, 6.12.96 and others. If you are running Linux kernel 5.15 or later up to the fix versions, apply the relevant patch for your kernel branch.

Is CVE-2026-64399 actively exploited?

CVE-2026-64399 has not been confirmed as actively exploited and is not listed in the CISA KEV catalog.

CVE-2026-64399

Critical

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.

Package Linux Kernel

Published 2026-07-25

Last modified 2026-09-04

CVSS version 3.1

Patch available

Yes

CVSS 3.1 score

9.8

out of 10

Critical

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

High

Availability

High

Vector string

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

Affected versions

Linux kernel versions 5.15 and later are affected. Fixed in 6.1.178, 6.6.145, 6.12.96, 6.18.39, 7.1.4, 7.2 and their respective stable series.

Affected from

≥ 5.15

Fixed in

✓ 6.1.178 6.1.x ✓ 6.6.145 6.6.x ✓ 6.12.96 6.12.x ✓ 6.18.39 6.18.x ✓ 7.1.4 7.1.x ✓ 7.2

References

6 total

Kernel Git
https://git.kernel.org/stable/c/388e4139db27a9e3612c9d356b826f5b1ff6a9e3

Patch
Kernel Git
https://git.kernel.org/stable/c/620d133d469295ee7c017ca6aafac335f65c4a5a

Patch
Kernel Git
https://git.kernel.org/stable/c/9b9cf7e65cbeaae1b6636144bacee611cdd7a5d6

Patch
Kernel Git
https://git.kernel.org/stable/c/baae7b39673ec21073a25e3d14f8feaada01d5df

Patch
Kernel Git
https://git.kernel.org/stable/c/bf460ad5958d506492de4524a656439da3f99c51

Patch

Showing 5 of 6 references View all on NVD

Details

CVE ID CVE-2026-64399

Severity Critical

CVSS score 9.8 / 10

CVSS version 3.1

Published 2026-07-25

Modified 2026-09-04

KEV No

Patch

Yes

Package linux

Frequently asked questions

What is CVE-2026-64399?

CVE-2026-64399 is a Critical severity Linux kernel vulnerability with a CVSS score of 9.8 out of 10 . It affects Linux kernel versions from 5.15 onward and has been patched in 6.1.178, 6.6.145, 6.12.96 and others. CVE-2026-64399 has not been confirmed as actively exploited and is not listed in the CISA KEV catalog.
What is the CVSS score for CVE-2026-64399?

CVE-2026-64399 has a CVSS score of 9.8 out of 10, rated Critical severity (CVSS 3.1). The vector string is CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.
Is there a patch available for CVE-2026-64399?

Yes. CVE-2026-64399 has been patched. Fixed versions include 6.1.178, 6.6.145, 6.12.96 and others. If you are running Linux kernel 5.15 or later up to the fix versions, apply the relevant patch for your kernel branch.
Is CVE-2026-64399 actively exploited?

No. CVE-2026-64399 has not been confirmed as actively exploited. It is not listed in the CISA Known Exploited Vulnerabilities (KEV) catalog.