[CVE-2026-98453][MODERATE REGULAR] smb: client: close handle after create-context parsing failure [ Upstream

[CVE-2026-98453][MODERATE REGULAR] smb: client: close handle after create-context parsing failure [ Upstream

[AL-KERNEL]

CVE: CVE-2026-98453
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: smb: client: close handle after create-context parsing failure [ Upstream
Commit: 80c67cc71d32ccafc89a29b669243b40d81b930f
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=80c67cc71d32ccafc89a29b669243b40d81b930f
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98453
Analysis date: Sat, 24 Oct 2026 13:19:28 -0400
ActionableScore: 3
ActionableScore lower bound: unknown
Actionable bucket: Ordinary Moderate
Manual review required: NO

Summary:
A malicious SMB server can cause persistent server-handle and client open-count leakage by returning malformed CREATE contexts, with only limited availability impact demonstrated.

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

The original Linux kernel CVE announcement for CVE-2026-98453 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98453

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 REGULAR
Manual review required: NO

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

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

CVE-2026-98453	MODERATE	https://www.kernelcve.org/list/?q=CVE-2026-98453 CHECK WITH IMPACT FROM ORIG NN LOW | AEGIS IMPACT MODERATE AEGIS_AS=3 LEGACY=MODERATE RESULT=SAME (final reconciliation agrees; DECISION: both MODERATE)	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:L';*CWE-772;CWE-404;BEST CVSS score: '4.3';DESCR 'SMB2_open records a successful CREATE as a remote open before parsing the returned create contexts. If a server supplies malformed context data and smb2_parse_contexts rejects it, the client can return an error while leaving the server side handle open and num_remote_opens elevated. For the CVSS the PR:N value applies because a malicious or faulty SMB server does not need an authenticated local account on the client, although a client process or user must initiate an open against that server. The demonstrated primitive is persistent resource retention with limited availability impact. There is no supported UAF, OOB access, information disclosure, arbitrary write, kernel crash, or privilege escalation path. Automated impact decision path. The original SimpleNet classifier selected MODERATE_KPANIC. The primary LLM estimated paranoid CVSS 4.3 and the production ActionableScore returned 3 with recommendation Ordinary Moderate. The production rules then evaluated CVSS thresholds and ActionableScore thresholds. Recorded rule transitions were CVSS and initial triage stage MODERATE_KPANIC to MODERATE because the CVSS score, vector or bug class threshold rule was applied. The legacy KP specialist has no review artifact for this run. The legacy FD or DH downgrade specialist has no review artifact for this run. Exact triggered rule markers were DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS. The independent weaker Aegis shadow evaluated CVSS 4.3 and ActionableScore 3 with primitive class CLASS_C and manual review REQUIRED. Its independently reconciled impact was MODERATE. The shadow agreed with the final production impact and aggregation did not change that impact. The final reported impact is MODERATE.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 3)	MAYBE	OOB DISK SIMPLEFIX ERRORPATH SERVERTOCLIENT LINUS  DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS	-	-	checked

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

ActionableScore=3
PrimitiveClass=CLASS_C
RealUAF=NO
HostAdminRequired=NO
NamespaceScopedPrivilege=UNKNOWN
ImportantCandidate=NO
ManualReview=NO
AutoDowngradeAllowed=YES
RequiresHostUID0=NO
AuthorizationDecisionBypass=NO
ProtectedResourceImpact=NONE
B4PendingReview=NO
B4PendingConfirmed=NO

1. ActionableScore

* Raw base score: 3.
* Conservative score: 3; no floor or cap applied.
* Raw paranoid score: 3.
* Paranoid score: 3; no additional technically supported consequence.
* Final recommended bucket: **Ordinary Moderate**::

2. Signal breakdown

* +2 remote/network reachability: a malicious SMB server can return malformed CREATE contexts when a client initiates an open.
* +1 concrete persistent resource/reference leak: successful CREATE establishes a server handle and increments `num_remote_opens`, but parsing failure previously returned without `SMB2_close()`.
* No crash or extra availability point: only handle retention and accounting imbalance are demonstrated; host-wide exhaustion is not shown.
* No UAF, OOB access, kernel-memory write, disclosure, authorization bypass, or privilege escalation is evidenced.
* B5-R and B3-PENDING do not apply: there is no heap OOB write or shared-backing write.

3. Reachability analysis

The remote SMB server controls the malformed response, but client-side user interaction is required to connect and issue an open. The remote actor needs neither host UID 0 nor host-administrator capability. Privilege needed to establish the client mount/session is not supplied, but it is a deployment prerequisite rather than attacker privilege. Namespace scope is unresolved. No race, unusual hardware, or timing condition is involved.

4. Primitive and severity reading

The exact defect is an error-path remote-handle leak plus elevated local open accounting after a post-CREATE parsing failure. The fix explicitly closes the established handle. This is passive resource-retention behavior, classified CLASS_C rather than memory or active-object corruption. Repeated malformed replies could accumulate leaked resources, but material host-wide exhaustion is not established. There is no Important-grade primitive or unresolved security boundary, so automatic downgrade is allowed.

5. One-sentence report phrase

A malicious SMB server can cause persistent server-handle and client open-count leakage by returning malformed CREATE contexts, with only limited availability impact demonstrated.

6. Manual review advice

NO MANUAL CHECK NEEDED

The patch and commit fully identify a balanced-resource cleanup omission without a material unknown corruption or authorization primitive.

7. Call-site confidence

Call-site confidence: high

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

Patch: smb: client: close handle after create-context parsing failure [ Upstream
Commit: 80c67cc71d32ccafc89a29b669243b40d81b930f
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=80c67cc71d32ccafc89a29b669243b40d81b930f

Changed files:
  fs/smb/client/smb2pdu.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=80c67cc71d32ccafc89a29b669243b40d81b930f

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

The original Linux kernel CVE announcement for CVE-2026-98453 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98453

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: Not available
  The Best / paranoid CVSS vector: AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:L
  The Best / paranoid CVSS score: 4.3

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: unknown
  Paranoid ActionableScore: 3

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: NO
Published priority for this report (same as in Subject): MODERATE REGULAR

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).