CVE-2026-64399

Published Jul 25, 2026

Last updated 2 months ago

CVSS critical 9.8

Overview

Description
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.
Source
416baaa9-dc9f-4396-8d5f-8c081fb06d67
NVD status
Analyzed
Products
linux_kernel

Risk scores

CVSS 3.1

Type
Secondary
Base score
9.8
Impact score
5.9
Exploitability score
3.9
Vector string
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Severity
CRITICAL

Weaknesses

nvd@nist.gov
NVD-CWE-noinfo

Social media

Hype score
Not currently trending

  1. #CVE-2026-64399 - #Linux ksmbd missing permission checks on FSCTL_DUPLICATE_EXTENTS_TO_FILE. Allows data overwrite on read-only shares. #CVSS 0.0. No patch yet; monitor for updates. #CVE #devsecops #devops #developer #sysadmin #cybersecurity #infosec https://t.co/Y6Si1DS9sX

    @HugoValters

    25 Jul 2026

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Configurations

Related CVEs

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References

Sources include official advisories and independent security research.