CVE-2026-64399
Received Received - Intake

BaseFortify

Publication date: 2026-07-25

Last updated on: 2026-07-25

Assigner: kernel.org

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.

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Meta Information

Published
2026-07-25
Last Modified
2026-07-25
Generated
2026-07-25
AI Q&A
2026-07-25
EPSS Evaluated
N/A
NVD
CVE-2026-64399
EUVD
EUVD-2026-48943

Affected Vendors & Products

Showing 1 associated CPE
Vendor Product Version / Range
linux_kernel linux_kernel *

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Exploitability

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CWE ID Description
CWE-UNKNOWN

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Executive Summary

This vulnerability in the Linux kernel involves a flaw in the ksmbd module where the FSCTL_DUPLICATE_EXTENTS_TO_FILE operation allows overwriting file data without proper permission checks. The issue occurs because the operation bypasses share-level and per-handle write checks that other write operations enforce.

Impact Analysis

An attacker could exploit this to overwrite data on a read-only share or modify files using a handle with only FILE_WRITE_ATTRIBUTES permissions. This could lead to data corruption, unauthorized changes, or potential privilege escalation depending on the affected system.

Compliance Impact

This vulnerability could violate compliance requirements that mandate data integrity and access controls, such as GDPR's data protection principles or HIPAA's security rules. Unauthorized data overwrites may lead to breaches of confidentiality or integrity, triggering regulatory penalties.

Mitigation Strategies

Update the Linux kernel to the latest patched version to resolve the ksmbd FSCTL_DUPLICATE_EXTENTS_TO_FILE permission check vulnerability.

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