[CVE-2026-90375][MODERATE REGULAR] wifi: mt76: fix non-AQL packet accounting for MLO stations [ Upstream

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

CVE: CVE-2026-90375
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: wifi: mt76: fix non-AQL packet accounting for MLO stations [ Upstream
Commit: f85f6933cc170155f1c7c2dffdd014965787c71b
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=f85f6933cc170155f1c7c2dffdd014965787c71b
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90375
Analysis date: Thu, 17 Sep 2026 17:30:49 -0400
ActionableScore: 3
ActionableScore lower bound: 2
Actionable bucket: Borderline / manual review recommended
Manual review required: YES

Summary:
No one-sentence report phrase was found.

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

The original Linux kernel CVE announcement for CVE-2026-90375 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90375

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
======================================================================

CVE-2026-90375	MODERATE	https://www.kernelcve.org/list/?q=CVE-2026-90375 CHECK WITH IMPACT FROM ORIG NN LOW	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L';CWE-682;**CWE-400;CWE-841;Other CVSS 'AV:A/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '4.3';DESCR 'The mt76 TX path can account non AQL packets on the wrong WCID for WiFi MLO stations because __mt76_tx_queue_skb overwrites the driver supplied WCID with sta drv_priv after TX selection. In a multi link case, traffic sent on one link can increment the counter on another link and decrement a different counter, causing non_aql_packets to become permanently inflated. Once the counter exceeds MT_MAX_NON_AQL_PKT, the TX scheduler can refuse to service the affected station, causing an adjacent WiFi denial of service for that station. For the CVSS the PR:N is used for the paranoid score when an open or weakly controlled WiFi deployment allows an adjacent MLO station to trigger the behavior without prior privileges on the target. The realistic base case is PR:L because the attacker usually must be an associated or otherwise authorized WiFi station. The issue is adjacent network reachable over WiFi, not Internet reachable. Impact is availability loss for station TX service only, with no evidence of memory corruption, information disclosure, or privilege escalation.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline / manual review recommended (with actual score 3)	YES	REMOTE NETWORK PACKET  DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS	NO	NO	checked

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

ActionableScore=3
ActionableScoreLower=2
PrimitiveClass=NONE
RealUAF=NO
HostAdminRequired=NO
NamespaceScopedPrivilege=NO
ImportantCandidate=NO
ManualReview=RECOMMENDED
AutoDowngradeAllowed=YES

1. ActionableScore

* Raw conservative score: 2
* Conservative score: 2
* Raw paranoid score: 3
* Paranoid score: 3
* Final recommended bucket: **Borderline / manual review recommended**::

No floor or cap changed the score.

2. Signal breakdown

Conservative positive signals:

* +1 Adjacent WiFi data-plane reachability. The trigger appears to be station traffic in an MLO setup, not host-local administrative control.
* +1 Limited availability impact. Wrong non_aql_packets accounting can cause the TX scheduler to stop servicing the affected station.

Paranoid positive signals:

* +2 Network-style reachability within adjacent WiFi range. In an open or weakly controlled WiFi deployment, an adjacent MLO station may be able to trigger the behavior without prior privileges on the target host.
* +1 Limited availability impact. The practical consequence remains denial of service for station TX service.

Non-awarded signals:

* No UAF, double free, refcount corruption, OOB access, or memory corruption is established.
* No controlled reclaim, arbitrary write, information disclosure, or privilege escalation is demonstrated.
* No host-wide kernel crash or panic is established.
* No extra availability point is awarded because the observed effect is limited to scheduler refusal for the affected station.
* No security-boundary bypass is established.
* No resource exhaustion beyond the specific accounting/scheduling failure is established.

Negative signals:

* No privilege penalty is applied. Host-admin-equivalent privilege is not required for the described station-side traffic trigger.
* No rare-hardware penalty is applied. The bug is hardware/driver-specific, but the supplied evidence does not establish rare or physical-only access beyond normal WiFi adjacency.
* No race/timing penalty is applied. The issue is a deterministic accounting logic bug, not a narrow race.

3. Reachability analysis

The likely attacker is an adjacent WiFi station participating in or able to send traffic for an MLO scenario. The conservative interpretation assumes the attacker may need to be an associated or otherwise authorized station, but this is still below host-admin privilege. The paranoid interpretation treats open or weakly controlled WiFi deployments as allowing PR:N-style triggering from an adjacent station.

The issue is not Internet reachable. It is reachable over the local wireless medium when the vulnerable mt76 MLO path is active. No namespace-scoped privilege is involved. No host sysctl, boot option, or host administrative setup is shown as part of the attacker-controlled trigger, beyond the device and MLO feature being in use. No special race repeatability issue is indicated.

4. Primitive and severity interpretation

The exact primitive is incorrect accounting of non-AQL packets on the wrong WCID after __mt76_tx_queue_skb overwrites the driver-supplied WCID with sta drv_priv. This is a logic/accounting bug, not a kernel memory lifetime or corruption bug.

The affected object is active driver scheduling/accounting state, but the stale-use and memory-corruption rules do not apply. There is no concrete repeated release/refcount operation. There is no first lifetime-ending operation, no surviving dangling reference, and no second lifetime mutation.

PrimitiveClass=NONE because the patch establishes no meaningful corruption, ownership, authorization, lifetime, or semantic reinterpretation primitive. The demonstrated consequence is denial of service for the affected station due to TX scheduler refusal after the counter becomes permanently inflated. Stronger consequences such as host crash, information disclosure, or privilege escalation are speculative and not supported by the patch.

ImportantCandidate=NO because this is a limited adjacent availability issue without memory corruption or boundary bypass. AutoDowngradeAllowed=YES because no unresolved Important-grade primitive remains. Operational severity is Low to borderline Moderate, with manual review mainly justified by adjacent-network reachability and WiFi deployment variability.

5. One-sentence report phrase

Wrong WCID selection in the mt76 MLO TX path can inflate non AQL packet accounting for a station and make the TX scheduler stop servicing that station, causing adjacent WiFi denial of service without evidence of memory corruption or privilege escalation.

6. Manual review recommendation

MANUAL CHECK RECOMMENDED

Reason: the issue is adjacent-network reachable over WiFi and deployment-dependent, but the established impact is limited DoS for affected station traffic with no kernel corruption or security-boundary primitive.

7. Call-site confidence

Call-site confidence: medium

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

Patch: wifi: mt76: fix non-AQL packet accounting for MLO stations [ Upstream
Commit: f85f6933cc170155f1c7c2dffdd014965787c71b
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=f85f6933cc170155f1c7c2dffdd014965787c71b

Changed files:
  drivers/net/wireless/mediatek/mt76/tx.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=f85f6933cc170155f1c7c2dffdd014965787c71b

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

The original Linux kernel CVE announcement for CVE-2026-90375 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90375

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:A/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L
  The Best / paranoid CVSS vector: AV:A/AC:L/PR:N/UI:N/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: 2
  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).