[CVE-2023-52441][MODERATE 7.0] ksmbd: fix out of bounds in init_smb2_rsp_hdr() [ Upstream

[CVE-2023-52441][MODERATE 7.0] ksmbd: fix out of bounds in init_smb2_rsp_hdr() [ Upstream

[AL-KERNEL]

CVE: CVE-2023-52441
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: ksmbd: fix out of bounds in init_smb2_rsp_hdr() [ Upstream
Commit: 5c0df9d30c289d6b9d7d44e2a450de2f8e3cf40b
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=5c0df9d30c289d6b9d7d44e2a450de2f8e3cf40b
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2023-52441
Analysis date: Tue, 22 Sep 2026 17:45:50 -0400
ActionableScore: 6
ActionableScore lower bound: 5
Actionable bucket: Actionable Moderate / Strong Important candidate requiring manual review
Manual review required: YES

Summary:
No one-sentence report phrase was found.

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

The original Linux kernel CVE announcement for CVE-2023-52441 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2023-52441

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: MODERATE 7.0
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-2023-52441	MODERATE	https://www.kernelcve.org/list/?q=CVE-2023-52441 CHECK WITH IMPACT FROM ORIG NN NONE	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:H';CWE-125;*CWE-20;CWE-843;Other CVSS 'AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '8.6';DESCR 'A protocol state validation flaw in ksmbd allows an SMB1 negotiate packet to enter the SMB2 processing path after an earlier SMB2 negotiation has cleared need_neg. The SMB1 request can then be interpreted as an SMB2 request and reach init_smb2_rsp_hdr with an incompatible packet layout, resulting in an out of bounds access. A remote client can trigger the condition by sending an SMB2 negotiate request followed by an SMB1 negotiate request. For the CVSS the PR:N value is selected because the sequence can be sent before normal SMB authentication and requires only network reachability to the ksmbd service. The issue is network reachable when ksmbd is enabled and its SMB listener is accessible, commonly over TCP port 445. Impact is at least remote denial of service through a kernel crash. In the paranoid interpretation the out of bounds processing may also cause limited confidentiality or integrity impact and should be reviewed manually, although a controlled information leak or write primitive is not established. ksmbd is commonly exposed on local file sharing or data center networks, but Internet exposed SMB services would also be reachable.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate / Strong Important candidate requiring manual review (with actual score 6) 	MAYBE	REMOTE WRITE OOB DISK INIT SKIP CVEOUTDATED PACKET  KPANIC INCREASED_TO_HIGH_BASED_ON_GUESSCVSS8.5PLUS DECREASED_TO_MODERATE7_BASED_ON_FALSEPOSCHECKOFDH	-	-	checked

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

ActionableScore=6
ActionableScoreLower=5
PrimitiveClass=CLASS_A
RealUAF=NO
HostAdminRequired=NO
NamespaceScopedPrivilege=UNKNOWN
ImportantCandidate=YES
ManualReview=REQUIRED
AutoDowngradeAllowed=NO

1. ActionableScore

* Raw conservative score: 5
* Conservative score: 5
* Raw paranoid score: 6
* Paranoid score: 6
* No floor or cap was applied.
* Final recommended bucket: **Actionable Moderate / Strong Important candidate requiring manual review**::

2. Signal breakdown

Conservative signals:

* +2 Remote reachability. An unauthenticated network client can send SMB2 NEGOTIATE followed by SMB1 NEGOTIATE to an exposed ksmbd listener.
* +2 Strong attacker-influenced semantic reinterpretation. Attacker-controlled SMB1 bytes are accepted after SMB2 negotiation and processed under incompatible SMB2 semantics, reaching `init_smb2_rsp_hdr()`.
* +1 Reliable kernel crash or strong DoS. The resulting kernel out-of-bounds access provides a realistic remote crash path.
* Total: 5.

Paranoid signal:

* +1 Semantic reinterpretation affects memory access. The incompatible packet layout reaches a function that performs an established out-of-bounds access. This preserves concern about a stronger memory effect pending inspection of the exact access and downstream use.
* Total: 6.

Not awarded:

* No UAF, stale-object use, or repeated lifetime mutation is established.
* No controlled reclaim, arbitrary write, attacker-selected overwrite target, or callback influence is demonstrated.
* No confidentiality point is awarded because no kernel bytes are shown to reach the client.
* No integrity point is awarded because the supplied code does not establish an out-of-bounds write or modification of protected state.
* No additional availability point is awarded because it would duplicate the same kernel-crash consequence.
* No common networking-core bonus is awarded because ksmbd is an optional server subsystem rather than a universal packet-processing path.
* No configuration penalty is applied merely because ksmbd must be enabled.

3. Reachability analysis

The evaluated attacker is a remote, unauthenticated SMB client. The client controls the complete trigger sequence by opening a connection, sending an SMB2 negotiation request, and then sending an SMB1 negotiation request after `need_neg` becomes false. No SMB login, local process, capability, namespace privilege, or host-administrator access is required for the attacker.

A host administrator must previously enable and expose ksmbd, but that is ordinary service deployment rather than attacker privilege. Therefore, `HostAdminRequired=NO`. Namespace-scoped privilege is not relevant to the direct network trigger and cannot be resolved from the supplied patch, so it remains `UNKNOWN`.

No special hardware, boot mode, race, or narrow timing window is required. The trigger is an ordered protocol sequence and appears repeatable. Exposure depends on whether the ksmbd listener, commonly TCP port 445, is reachable from the attacker.

4. Primitive and severity interpretation

The exact primitive is attacker-controlled protocol semantic confusion followed by an out-of-bounds access. After SMB2 negotiation, the vulnerable code skips protocol validation when `need_neg` is false. A subsequent SMB1 packet therefore remains associated with SMB2 operations and can reach `init_smb2_rsp_hdr()` with an incompatible structure layout.

This is not a UAF and does not involve stale storage or cleanup-only lifetime processing. It is `CLASS_A` because the same attacker-controlled representation is accepted as SMB1 input but later consumed under materially different SMB2 semantics, directly causing an active memory-access violation.

The demonstrated practical consequence is remote kernel DoS. A disclosure or write primitive is not established, so privilege escalation and remote code execution remain speculative. Manual inspection of `init_smb2_rsp_hdr()` and its callers is required to determine whether the OOB operation is read-only, whether read data can enter the response, or whether any subsequent indexing or write can affect kernel state.

`ImportantCandidate=YES` reflects the pre-authentication remote semantic-reinterpretation primitive. `AutoDowngradeAllowed=NO` because automatically treating the issue as ordinary crash-only behavior could discard an unresolved attacker-controlled OOB primitive.

5. One-sentence report phrase

An unauthenticated remote client can switch from SMB2 to SMB1 after negotiation and cause ksmbd to interpret an incompatible SMB1 packet through the SMB2 response path, resulting in an out-of-bounds kernel access and potential host denial of service.

6. Manual review recommendation

MANUAL CHECK REQUIRED

Review the exact OOB operation and response construction path for disclosure, attacker-influenced indexing, or write effects beyond the demonstrated remote crash.

7. Call-site confidence

Call-site confidence: medium

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

Patch: ksmbd: fix out of bounds in init_smb2_rsp_hdr() [ Upstream
Commit: 5c0df9d30c289d6b9d7d44e2a450de2f8e3cf40b
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=5c0df9d30c289d6b9d7d44e2a450de2f8e3cf40b

Changed files:
  fs/ksmbd/server.c
  fs/ksmbd/smb_common.c
  fs/ksmbd/smb_common.h

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=5c0df9d30c289d6b9d7d44e2a450de2f8e3cf40b

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

The original Linux kernel CVE announcement for CVE-2023-52441 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2023-52441

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:L/PR:N/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS vector: AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:H
  The Best / paranoid CVSS score: 8.6

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: 5
  Paranoid ActionableScore: 6

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: MODERATE
KPANIC detected for this report: YES
Published priority for this report (same as in Subject): MODERATE 7.0

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).