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Review reviewCritical

CVE-2026-64399

Linux

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 ha...

CVSS
9.8
EPSS
-
- percentile
CISA KEV
Not listed
Published
2026.07.25
PRIORITY ASSESSMENT

Review review

The CVSS severity warrants an early asset and exposure review.

Known exploitationNot established by KEV
Exploit probability-
Technical severityCVSS 9.8

Vulnerability overview

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 ha...

Affected product and versions

Product
Linux
Affected versions
>= eb817368f50c1cbe1bd07044124aad7db6330e3a < bf460ad5958d506492de4524a656439da3f99c51, >= eb817368f50c1cbe1bd07044124aad7db6330e3a < 620d133d469295ee7c017ca6aafac335f65c4a5a, >= eb817368f50c1cbe1bd07044124aad7db6330e3a < 9b9cf7e65cbeaae1b6636144bacee611cdd7a5d6, >= eb817368f50c1cbe1bd07044124aad7db6330e3a < baae7b39673ec21073a25e3d14f8feaada01d5df, >= eb817368f50c1cbe1bd07044124aad7db6330e3a < c917e4522d251071dde9871b9142d8ea1186ebfe, >= eb817368f50c1cbe1bd07044124aad7db6330e3a < 388e4139db27a9e3612c9d356b826f5b1ff6a9e3, >= 5.15
Fixed versions
No verified fixed-version field is available yet

Recommended response sequence

Confirm exposure before applying a vendor-supported change.

Full remediation guide
  1. 1
    Identify

    Confirm that Linux and an affected version are present.

  2. 2
    Prioritize

    Combine exploitation signals with asset exposure and business criticality.

  3. 3
    Remediate

    Follow the vendor advisory or supported update path and preserve rollback options.

  4. 4
    Verify

    Recheck the version, service health, access paths, and relevant logs.

Technical data

CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
CWE
Not available