[CVE-2026-98957][MODERATE REGULAR] wifi: mt76: mt7915: disable rx napi when removing device [ Upstream

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

CVE: CVE-2026-98957
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: wifi: mt76: mt7915: disable rx napi when removing device [ Upstream
Commit: 0281dac1e213329b053fb02e612de7f1477a52d7
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=0281dac1e213329b053fb02e612de7f1477a52d7
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98957
Analysis date: Mon, 26 Oct 2026 16:30:51 -0400
ActionableScore: 1
ActionableScore lower bound: unknown
Actionable bucket: Ordinary Moderate
Manual review required: NO

Summary:
Host-privileged mt7915 teardown can leave RX NAPI active while its backing structures are destroyed, enabling a constrained teardown UAF and kernel instability.

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

The original Linux kernel CVE announcement for CVE-2026-98957 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98957

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.

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

CVE-2026-98957	MODERATE	https://www.kernelcve.org/list/?q=CVE-2026-98957 CHECK WITH IMPACT FROM ORIG NN IMPORTANT | AEGIS IMPACT MODERATE_KPANIC AEGIS_AS=0 LEGACY=MODERATE RESULT=DIFF (final Legacy and Aegis differ; FINAL: MODERATE, Aegis: MODERATE_KPANIC)	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:H/UI:N/S:U/C:L/I:L/A:H';*CWE-672;CWE-362;*CWE-416;Other CVSS 'AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '5.2';DESCR 'The mt7915 teardown path can leave RX NAPI enabled while DMA queues and related resources are being cleaned up. This causes warnings during NAPI and page pool destruction and can make the system unstable after the module is reinserted. An active RX handler overlapping teardown may access freed structures, making this a lifecycle race and a potential use after free rather than only a harmless warning. No specific arbitrary write or information disclosure primitive is demonstrated. For the CVSS the PR:H value is selected because reliable triggering normally requires permission to unload the mt7915e module, remove the device, or control a failing probe path. The issue is not directly network reachable and ordinary WiFi traffic alone is not shown to trigger teardown. Automated impact decision path. The original SimpleNet classifier selected IMPORTANT. The primary LLM estimated paranoid CVSS 5.2 and the production ActionableScore returned 1 with recommendation Ordinary Moderate. The production rules then evaluated CVSS thresholds and ActionableScore thresholds. Recorded rule transitions were CVSS and initial triage stage IMPORTANT to MODERATE_KPANIC because the CVSS score, vector or bug class threshold rule was applied. ActionableScore thresholds stage MODERATE_KPANIC to MODERATE because the ActionableScore 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 LOWERED_FROM_HIGH_BASED_ON_GUESSCVSS and DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN4 and V41_INHERITED_KPANIC_PROMOTION_BLOCKED and MANUAL_REVIEW_REQUIRED. The independent weaker Aegis shadow evaluated CVSS 2.1 and ActionableScore 0 with primitive class CLASS_C and manual review REQUIRED. Its independently reconciled impact was MODERATE_KPANIC. The models disagreed but the aggregation rules retained the production result. The final reported impact is MODERATE.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 1)	MAYBE	REMOTE UAF NETWORK HARDWARE  LOWERED_FROM_HIGH_BASED_ON_GUESSCVSS  DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN4 V41_INHERITED_KPANIC_PROMOTION_BLOCKED MANUAL_REVIEW_REQUIRED	-	-	checked

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

ActionableScore=1
PrimitiveClass=CLASS_B
RealUAF=YES
HostAdminRequired=YES
NamespaceScopedPrivilege=NO
ImportantCandidate=NO
ManualReview=RECOMMENDED
AutoDowngradeAllowed=YES
RequiresHostUID0=UNKNOWN
AuthorizationDecisionBypass=NO
ProtectedResourceImpact=NONE
B4PendingReview=NO
B4PendingConfirmed=NO

1. ActionableScore

* Raw base score: 1.
* Conservative score: 1; no floor or cap applied.
* Raw paranoid score: 1.
* Paranoid score: 1; no additional exploit primitive is supported.
* Final recommended bucket: **Ordinary Moderate**::

2. Signal breakdown

* +2 Real lifetime violation: RX NAPI remains active while DMA queues and related structures are destroyed; the commit explicitly identifies RX handlers accessing freed structures.
* +1 Reliable kernel crash/strong DoS concern: teardown produces warnings and post-reinsertion instability, while a freed-structure access plausibly causes an Oops.
* -2 Host-administrator-equivalent trigger: the grounded trigger is module unload/device removal, normally requiring host-level module or device-management authority.
* No extra Availability point: instability and a possible crash are the same availability consequence.
* No structured stale-object leverage: no consumed pointer, length, callback, or attacker-shaped reclaimed object is identified.
* No controlled reclaim, arbitrary write, disclosure, authorization bypass, or remote packet trigger is shown.
* NEW52/B5-R and NEW53/B3-PENDING do not apply: there is no retry-accumulated OOB write or shared-backing write.

3. Reachability analysis

The demonstrated path is unloading/reloading mt7915e or device teardown. Ordinary Wi-Fi traffic cannot initiate teardown. Module removal and device removal normally require effective host-administrator powers. The probe-error path is covered defensively by the fix, but no attacker-invocable below-admin method for forcing the relevant failure is supplied. No namespace-scoped complete trigger is shown, and the affected MT7915/MT7916 hardware must be present. No narrow race penalty is applied because the patch does not establish that the teardown overlap is difficult to reproduce.

4. Primitive and severity reading

This is an asynchronous teardown lifetime violation involving active RX/NAPI processing, not a fixed passive buffer. NAPI can continue running after associated DMA/RX structures are freed. The shown effects are warnings and system instability; a stale RX-handler dereference is clearly implied. No second release/refcount mutation or useful post-reclamation field consumption is shown. It is therefore constrained CLASS_B rather than CLASS_A. Host-admin gating and teardown-only evidence make ImportantCandidate=NO and permit downgrade, while the real lifetime defect still merits review.

5. One-sentence report phrase

Host-privileged mt7915 teardown can leave RX NAPI active while its backing structures are destroyed, enabling a constrained teardown UAF and kernel instability.

6. Manual review advice

MANUAL CHECK RECOMMENDED

Confirm whether any non-admin hot-unplug, recovery, or probe-failure interface can drive the complete teardown sequence.

7. Call-site confidence

Call-site confidence: medium

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

Patch: wifi: mt76: mt7915: disable rx napi when removing device [ Upstream
Commit: 0281dac1e213329b053fb02e612de7f1477a52d7
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=0281dac1e213329b053fb02e612de7f1477a52d7

Changed files:
  drivers/net/wireless/mediatek/mt76/mt7915/init.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=0281dac1e213329b053fb02e612de7f1477a52d7

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

The original Linux kernel CVE announcement for CVE-2026-98957 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98957

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:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS vector: AV:L/AC:H/PR:H/UI:N/S:U/C:L/I:L/A:H
  The Best / paranoid CVSS score: 5.2

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: 1

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).