[CVE-2026-98452][MODERATE REGULAR] smb: client: clean up failed cached directory opens

[AL-KERNEL <alkernel@kernelcve.org>]

CVE: CVE-2026-98452
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: smb: client: clean up failed cached directory opens
Commit: 48958ddda3d7eee3600261e2d90671f63e055dc4
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=48958ddda3d7eee3600261e2d90671f63e055dc4
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98452
Analysis date: Sat, 24 Oct 2026 04:36:43 -0400
ActionableScore: 3
ActionableScore lower bound: unknown
Actionable bucket: Borderline / manual review recommended
Manual review required: YES

Summary:
An attacker-controlled SMB server can make a compound request partially succeed and then fail, causing the client to lose cleanup information for the resulting remote directory handle.

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

The original Linux kernel CVE announcement for CVE-2026-98452 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98452

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: YES

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

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AL-KERNEL CLASSIFICATION RESULT
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CVE-2026-98452	MODERATE	https://www.kernelcve.org/list/?q=CVE-2026-98452 CHECK WITH IMPACT FROM ORIG NN LOW | AEGIS IMPACT MODERATE AEGIS_AS=2 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-20;CWE-703;Other CVSS 'AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:N/A:L';BEST CVSS score: '4.3';DESCR 'The SMB client can lose track of a remote directory handle when CREATE succeeds but a later operation in the compound request fails. The missing FID prevents common cleanup from issuing the correct SMB2 close and repeated failures may retain server resources. An invalid or incomplete CREATE response could also be treated as usable state lacking explicit length and status validation. For the CVSS the PR:N value reflects that an attacker controlling the SMB server needs no privileges on the client, although the client must connect to the attacker controlled or compromised share. No UAF, OOB write, arbitrary write, information leak, or privilege escalation primitive is demonstrated. Availability impact is limited because reliable host wide exhaustion from repeated handle retention is not established. 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 Borderline / manual review recommended. 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 0.0 and ActionableScore 2 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.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline / manual review recommended (with actual score 3)	MAYBE	LOCK DISK INIT SERVERTOCLIENT LINUS  DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS	-	-	checked

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

ActionableScore=3
PrimitiveClass=NONE
RealUAF=NO
HostAdminRequired=UNKNOWN
NamespaceScopedPrivilege=UNKNOWN
ImportantCandidate=NO
ManualReview=RECOMMENDED
AutoDowngradeAllowed=YES
RequiresHostUID0=UNKNOWN
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; stronger consequences are unsupported.
* Final recommended bucket: **Borderline / manual review recommended**::

2. Signal breakdown

* +2 Remote/server-controlled response path: a malicious or compromised SMB server can return a successful CREATE followed by a failing compound response after the client connects.
* +1 Concrete resource leak: the successful CREATE acquires a remote FID, but the old early error exit loses the identifiers needed for `SMB2_close()`.
* +0 Malformed-response validation: missing length/status checks allowed invalid CREATE fields to be consumed, but no specific OOB access, UAF, disclosure, or corrupt sink is shown.
* +0 Availability: repeated leaked server handles are plausible, but reliable client-host exhaustion, kernel crash, or persistent host-wide denial of service is not established.
* No B5-R: there is no confirmed retry-accumulated heap OOB write or later consumption of corrupted heap state.
* No B3-PENDING: no shared/file-backed storage write is present.
* No authorization signal: response validation and handle cleanup do not change a security decision from DENY to ALLOW.

3. Reachability analysis

The credible actor is an attacker-controlled SMB server, with victim interaction or configuration needed to connect the client to its share. The patch does not establish whether mounting or otherwise arranging the complete client path requires host administration, a preconfigured mount, or an unprivileged user-accessible SMB facility; therefore host privilege and namespace scope remain unknown. No race, special hardware, or retry accumulation is required.

4. Primitive and severity reading

The exact defect is failed ownership/accounting transfer for a successfully opened remote directory handle, plus insufficient validation of its CREATE response. The fix records the FIDs, marks and counts the handle as open, and lets common cleanup close it after a later compound failure. This is not a UAF, heap overwrite, authorization bypass, or demonstrated active structured-state corruption. The shown consequence is a remote-handle leak; host-wide resource exhaustion remains speculative. Accordingly, there is no Class A/B/C corruption primitive and no Important-preserving unknown exploit chain.

5. One-sentence report phrase

An attacker-controlled SMB server can make a compound request partially succeed and then fail, causing the client to lose cleanup information for the resulting remote directory handle.

6. Manual review advice

MANUAL CHECK RECOMMENDED

Confirm whether repeated failures can consume meaningful client-side resources or only resources controlled by the malicious SMB server.

7. Call-site confidence

Call-site confidence: high

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

Patch: smb: client: clean up failed cached directory opens
Commit: 48958ddda3d7eee3600261e2d90671f63e055dc4
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=48958ddda3d7eee3600261e2d90671f63e055dc4

Commit description:

open_cached_dir() sends CREATE and QUERY_INFO as a compound request. If
the CREATE succeeds but a later command returns an error, the function
must retain the CREATE FID so common cleanup can issue SMB2_close(). It
also must not treat a response error as a valid CREATE.

Validate the CREATE response before using its fields, record the FIDs, and
mark the handle open before handling errors from later compound commands.
Move the -EREMCHG reconnect handling before response validation so a
missing response does not hide the reconnect request. Count the handle
when it is marked open; confirmed close responses decrement the counter,
while existing close retry behavior remains best effort on transport
failures.

Fixes: b0f6df7 ("cifs: cache FILE_ALL_INFO for the shared root handle")
Cc: stable@vger.kernel.org
Reported-by: Vega <vega@nebusec.ai>
Assisted-by: LLM
Co-developed-by: Luxing Yin <root@tr0jan.top>
Signed-off-by: Luxing Yin <root@tr0jan.top>
Signed-off-by: Zihan Xi <zihanx@nebusec.ai>
Tested-by: Frank Sorenson <sorenson@redhat.com>
Signed-off-by: Paulo Alcantara <pc@manguebit.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  fs/smb/client/cached_dir.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=48958ddda3d7eee3600261e2d90671f63e055dc4

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

The original Linux kernel CVE announcement for CVE-2026-98452 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98452

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:N/UI:R/S:U/C:N/I:N/A:L
  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).