[CVE-2026-68381][IMPORTANT] ksmbd: pin conn during async oplock break notification [ Upstream

[CVE-2026-68381][IMPORTANT] ksmbd: pin conn during async oplock break notification [ Upstream

[AL-KERNEL]

CVE: CVE-2026-68381
Priority: IMPORTANT
AL-KERNEL base severity: IMPORTANT
KPANIC flag: YES
Patch: ksmbd: pin conn during async oplock break notification [ Upstream
Commit: 0f72fc9659d7f585460d43c158055df5afdcffb6
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=0f72fc9659d7f585460d43c158055df5afdcffb6
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68381
Analysis date: Mon, 10 Aug 2026 14:24:22 -0400
ActionableScore: 7
ActionableScore lower bound: 4
Actionable bucket: Strong Important candidate / Actionable Moderate at minimum
Manual review required: YES

Summary:
A race in ksmbd async SMB2 oplock and lease break notification can leave queued work using a freed `ksmbd_conn`, allowing a network client with SMB session or share access to trigger a timing-dependent kernel UAF and likely remote DoS, with possible higher impact requiring manual review.

======================================================================
ABOUT THIS REPORT
======================================================================

The original Linux kernel CVE announcement for CVE-2026-68381 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68381

The original announcement does not normally provide a security severity
estimate, CVSS assessment, or enough information to determine whether the
reported kernel bug represents a practically relevant security issue.

This report was generated by AL-KERNEL, an AI-assisted Linux kernel
vulnerability analysis system developed by Alexander Larkin. It combines
an autonomous classifier with LLM-assisted technical analysis and a
separate ActionableScore mechanism.

The purpose of this report is to prioritize Linux kernel CVEs before
manual review, identify cases that require prompt investigation, and
support automatic closure of issues that are unlikely to have meaningful
security impact.

Published priority for this report: IMPORTANT
Manual review required: YES

A detailed explanation of the methodology and priority rules is included
at the end of this message.

======================================================================
AL-KERNEL CLASSIFICATION RESULT
======================================================================

CVE-2026-68381	IMPORTANT	CHECK WITH IMPACT FROM ORIG NN IMPORTANT	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H';*CWE-416;CWE-362;CWE-667;Other CVSS 'AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:H';BEST CVSS score: '7.5';DESCR 'An async SMB2 oplock or lease break notification in ksmbd can keep a raw ksmbd_conn pointer in queued work without holding a real object reference. If connection teardown races with that queued notification, the last connection reference can be dropped before the worker completes, and the worker can later use the freed connection in ksmbd_conn_write() or ksmbd_conn_r_count_dec(). For the CVSS the PR:L is used for the paranoid score because a practical trigger normally requires an SMB client context with access to a session or share that can create oplock or lease state and race it with disconnect or teardown. The issue is network reachable when ksmbd is exposed to the attacker, but exploitation is timing dependent and requires a teardown race with asynchronous notification work. Impact is at least remote denial of service via kernel crash and in the worst case may allow confidentiality or integrity impact due to kernel use-after-free memory corruption. YES REQUIRES MANUAL CHECK';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Strong Important candidate / Actionable Moderate at minimum (with actual score 6)  SKIP CVE-2026-68381 UNKNOWN SKIP No affected files built, so skip this CVE NO  - - unknown 	MAYBE	REMOTE WRITE OOB DISK RACE UAF SKIP  KPANIC INCREASED_TO_HIGH_BASED_ON_GUESSCVSS	-	-	checked

======================================================================
ACTIONABLESCORE ANALYSIS
======================================================================

ActionableScore=7
ActionableScoreLower=4

## 1. ActionableScore

* Conservative score: 4
* Paranoid score: 7
* Final recommended bucket: **Strong Important candidate / Actionable Moderate at minimum**::

## 2. Signal breakdown

Conservative signals:

* Remote reachable / network-triggerable: +2. ksmbd is an SMB server path and can be reached over the network when ksmbd is exposed.
* Memory corruption, weak primitive: +1. The bug is a race-dependent UAF of `struct ksmbd_conn`, but the patch does not demonstrate attacker-controlled reclaim or object replacement.
* Real lifetime corruption: +1. The async work stores a raw `ksmbd_conn` pointer without holding a real reference.
* Reliable kernel crash / strong DoS: +1. The worker may use the freed connection in `ksmbd_conn_write()` and `ksmbd_conn_r_count_dec()`.
* Hard or unreliable race / special timing required: -1. Triggering requires racing connection teardown with async oplock or lease break notification.

Paranoid additional signals:

* Memory corruption, strong primitive interpretation: +1 relative to conservative. The stale object is used after free and `ksmbd_conn_r_count_dec()` implies a write-like refcount operation on freed memory.
* Weak LPE concern: +1. The UAF occurs in a network server connection object and includes stale object use plus refcount/lifetime manipulation, but there is no demonstrated reclaim or controlled overwrite.
* Availability impact realistic: +1. If triggered, the impact is host kernel crash from a network-facing server path, not just a local process failure.

## 3. Reachability analysis

A remote SMB client with access to the ksmbd service can plausibly create oplock or lease state and then race disconnect or connection teardown against async break notification work. This is not a pure unauthenticated packet parser issue, so practical triggering likely requires at least an SMB client context with session or share access, matching PR:L in CVSS-style reasoning. Namespaces do not materially reduce the network exposure if ksmbd is bound to an attacker-reachable interface. ksmbd is not universally enabled by default like the TCP/IP core, but when deployed it is a directly network-exposed kernel server.

Call-site confidence: high. The patch and commit message identify both the producer paths and the async worker use sites.

## 4. Severity interpretation

This is more than an ordinary Moderate because it is a real kernel lifetime bug in a network-reachable server subsystem. Realistic evidence supports remote DoS with high race complexity. Theoretical impact may extend beyond DoS because the freed `ksmbd_conn` is later used by async worker code, including a refcount decrement path, but the patch does not show attacker-controlled reclaim, type confusion, callback control, or arbitrary write. Therefore the conservative score remains borderline, while the paranoid score reaches Strong Important candidate handling.

## 5. One-sentence report phrase

A race in ksmbd async SMB2 oplock and lease break notification can leave queued work using a freed `ksmbd_conn`, allowing a network client with SMB session or share access to trigger a timing-dependent kernel UAF and likely remote DoS, with possible higher impact requiring manual review.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED

Reason: this is a network-reachable kernel UAF involving async workqueue lifetime and connection teardown. Even though exploitation is race-dependent and no controlled reclaim primitive is shown, the combination of SMB server exposure, stale connection use, and refcount/lifetime manipulation should not be auto-closed.

======================================================================
UPSTREAM PATCH SUMMARY
======================================================================

Patch: ksmbd: pin conn during async oplock break notification [ Upstream
Commit: 0f72fc9659d7f585460d43c158055df5afdcffb6
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=0f72fc9659d7f585460d43c158055df5afdcffb6

Changed files:
  fs/smb/server/oplock.c

Diff excerpt:

Not included in this email. See the upstream URL for the full patch.

Full patch:
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=0f72fc9659d7f585460d43c158055df5afdcffb6

======================================================================
DETAILED REPORT METHODOLOGY
======================================================================

The original Linux kernel CVE announcement for CVE-2026-68381 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68381

The original CVE announcement normally does not include a security-level
estimate. In particular, it may not contain a CVSS assessment, an impact
level, or enough information to determine whether the reported bug is a
practically relevant security issue. One purpose of this parallel CVE list
is to provide that missing technical and prioritization information.

The original goal of the AL-KERNEL project was to prioritize Linux kernel
CVE analysis automatically before manual review. The system can also help
identify non-security issues that may be suitable for automatic closure.

This report was generated by AL-KERNEL, an AI-assisted Linux kernel
vulnerability analysis system developed by Alexander Larkin.

The first analysis stage combines an autonomous classifier with additional
LLM-based analysis. The autonomous classifier runs locally on a CPU and is
based on a backpropagation neural network. Together, these mechanisms
produce a technical vulnerability description, identify likely weakness
types, estimate CVSS severity, and provide input for ActionableScore.

Two CVSS estimates are retained because incomplete kernel vulnerability
information often permits more than one defensible interpretation:

  Conservative CVSS vector: AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:H
  The Best / paranoid CVSS vector: AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
  The Best / paranoid CVSS score: 7.5

The conservative vector represents a lower-impact interpretation.
The Best/paranoid vector intentionally represents a plausible upper-bound
interpretation and should not automatically be treated as demonstrated
real-world impact.

CVSS may also need to be adjusted for a particular Linux deployment,
because actual reachability, privileges, enabled kernel configuration,
hardware, namespaces, exposed device nodes, and other environmental
conditions can differ significantly between systems.

A separate ActionableScore mechanism evaluates practical remediation
urgency. Its analysis may include reachability, attack prerequisites,
subsystem exposure, memory-corruption characteristics, denial-of-service
reliability, and possible confidentiality, integrity, or
privilege-escalation impact.

  Conservative ActionableScore: 4
  Paranoid ActionableScore: 7

The final base severity is taken directly from the second tab-separated
field of the AL-KERNEL classification result. ActionableScore does not
replace or independently override that final AL-KERNEL decision, and
if ActionableScore adjusted impact level of ALKERNEL, then you would see
self-readable flags above like INCREASED_TO_HIGH_BASED_ON_ACTIONABLESCOREHIGHEREQTHAN7.

For an AL-KERNEL result of MODERATE, this report uses the following
additional presentation split:

  ActionableScore below 5   -> MODERATE REGULAR
  ActionableScore 5 or more -> MODERATE 7.0

The distinction between MODERATE REGULAR and MODERATE 7.0 makes it
possible to identify Moderate issues that should receive manual analysis
and fixes before lower-priority MODERATE REGULAR issues. In many cases,
MODERATE REGULAR fixes may wait for a later rebase or routine update.

There is one override in which MODERATE REGULAR becomes MODERATE 7.0
even when the ActionableScore is below 5. When the AL-KERNEL result
contains the KPANIC flag, a MODERATE result is always presented as
MODERATE 7.0. The KPANIC flag selected with few regexps without
usage of AI at all, so it helps to detect cases when Kernel Crash happens
and similar (to filter False-Negative results from the LLM usage).

KPANIC indicates that a reliable kernel crash, kernel panic, or similarly
serious kernel availability impact was identified by the classification
workflow.

AL-KERNEL base severity for this report: IMPORTANT
KPANIC detected for this report: YES
Published priority for this report (same as in Subject): IMPORTANT

These results are intended to support engineering triage. They are
machine-generated estimates, and cases marked for manual review should
be validated by a human security engineer before final disposition.
For more info read docs linked from here: https://kernelcve.org/
(and you can submit you own patch there to generate such a report
for non-existant CVE-id yet).

Note that in many cases this AI tool selects higher severity, than
real is (means you can expect Importants instead of Moderate 7.0 or
Moderates 7.0 instead of regular Moderates). If you see such cases,
please use reply email interface to add additional manual analyses
info to this particular CVE.
And please, please, let me know when you see Lows instead of Importants
or Important instead of Low (because particular for such cases I
need to tune this AI tool to make it better for this one and next similar).
My contact email for such notifications is alexanjelausa@gmail.com (and both
send reply to CVE record itself too and see "reply" button below for howto reply).