ksmbd: add permission checks for FSCTL_DUPLICATE_EXTENTS_TO_FILE (CVE-2026-64399) | HOL Guard CVE

Critical · CVSS 9.8CVE-2026-64399

ksmbd: add permission checks for FSCTL_DUPLICATE_EXTENTS_TO_FILE

Answer in brief

CVE-2026-64399 records a Critical severity (CVSS 9.8) vulnerability in ksmbd: add permission checks for FSCTL_DUPLICATE_EXTENTS_TO_FILE. The current sources do not mark it as known exploited. The current feed maps Linux/Linux (generic), Linux/Linux (generic). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Jul 25, 2026Updated Sep 4, 2026Source checked Sep 20, 2026First seen by HOL Aug 5, 2026Material review Sep 4, 2026

Upstream Advisory

Key facts

Risk: Critical · CVSS 9.8
Exploitation: Not marked as known exploited
Affected software: 3 mapped packages or products
Fix availability: Available

Why this deserves its current priority

CVSS is 9.8. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps Linux/Linux (generic), Linux/Linux (generic). Check affected ranges and fixed versions before updating.

Affected products and reported versions
Product	Affected versions	Fixed versions
cpe:2.3:o:linux:linux_kernel::::::::	Not reported	Not reported

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
Linux/Linuxgeneric	>=eb817368f50c1cbe1bd07044124aad7db6330e3a <bf460ad5958d506492de4524a656439da3f99c51 \|\| >=eb817368f50c1cbe1bd07044124aad7db6330e3a <620d133d469295ee7c017ca6aafac335f65c4a5a \|\| >=eb817368f50c1cbe1bd07044124aad7db6330e3a <9b9cf7e65cbeaae1b6636144bacee611cdd7a5d6 \|\| >=eb817368f50c1cbe1bd07044124aad7db6330e3a <baae7b39673ec21073a25e3d14f8feaada01d5df \|\| >=eb817368f50c1cbe1bd07044124aad7db6330e3a <c917e4522d251071dde9871b9142d8ea1186ebfe \|\| >=eb817368f50c1cbe1bd07044124aad7db6330e3a <388e4139db27a9e3612c9d356b826f5b1ff6a9e3	bf460ad5958d506492de4524a656439da3f99c51, 620d133d469295ee7c017ca6aafac335f65c4a5a, 9b9cf7e65cbeaae1b6636144bacee611cdd7a5d6, baae7b39673ec21073a25e3d14f8feaada01d5df, c917e4522d251071dde9871b9142d8ea1186ebfe, 388e4139db27a9e3612c9d356b826f5b1ff6a9e3
Linux/Linuxgeneric	5.15	Not reported

Recommended response

Check inventory. Check lockfiles and deployed manifests for Linux/Linux, Linux/Linux.
Review the reported fix. Update Linux/Linux to bf460ad5958d506492de4524a656439da3f99c51 if you use the affected versions. Test the change in a non-production environment first.

Evidence timeline and material changes

Published upstream
Jul 25, 2026
Evidence: source:cvelist:source_dates:source-dates:record
Source modified
Sep 4, 2026
Evidence: source:cvelist:source_dates:source-dates:record
First seen by HOL
Aug 5, 2026

Sources and claim methodology

Upstream source 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.

Quoted source text, attributed separately from HOL analysis.