[CVE-2026-98159][MODERATE 7.0] wifi: mt76: mt7921: validate CLC firmware records [ Upstream

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

CVE: CVE-2026-98159
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: wifi: mt76: mt7921: validate CLC firmware records [ Upstream
Commit: 602a950134ee2940136f60797e4457c3983b06ce
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=602a950134ee2940136f60797e4457c3983b06ce
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98159
Analysis date: Mon, 28 Sep 2026 13:22:31 -0400
ActionableScore: 5
ActionableScore lower bound: unknown
Actionable bucket: Actionable Moderate / Strong Important candidate requiring manual review
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-2026-98159 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98159

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.

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

CVE-2026-98159	MODERATE	https://www.kernelcve.org/list/?q=CVE-2026-98159 CHECK WITH IMPACT FROM ORIG NN IMPORTANT	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H';*CWE-20;CWE-125;*CWE-787;*CWE-835;Other CVSS 'AV:L/AC:L/PR:H/UI:N/S:U/C:L/I:L/A:H';BEST CVSS score: '6.7';DESCR 'The mt7921 CLC firmware loader trusted the region count, record lengths, and record indexes from a firmware image without sufficient bounds validation. A malformed image could move the region pointer before the firmware buffer, cause the record loop to stop advancing, copy data beyond the firmware boundary, or use clc idx to access phy clc outside its array. The unchecked array index provides a concrete out of bounds write primitive because a kernel pointer returned by devm_kmemdup can be stored beyond phy clc, potentially corrupting adjacent fields in the kernel structure. Impact is at least denial of service through a kernel crash, driver initialization failure, or an infinite loop. In the paranoid interpretation the memory corruption may also affect confidentiality and integrity or potentially support privilege escalation, although the written value and target location are constrained. For the CVSS the PR:H reflects that replacing the host firmware image or controlling driver firmware loading normally requires administrative privileges. The issue is not directly reachable through WiFi traffic and requires a malformed CLC firmware image to be installed and loaded on a system using the affected mt7921 driver.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate / Strong Important candidate requiring manual review (with actual score 5) 	MAYBE	REMOTE ERRORPATH NETWORK KPANIC  KPANIC LOWERED_FROM_HIGH_BASED_ON_GUESSCVSS_AND_PRH	-	-	checked

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

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

1. ActionableScore

* Raw conservative score: 2
* Conservative score: 5
* Raw paranoid score: 2
* Paranoid score: 5
* Applied conservative manual-review safety floor: 2 -> 5 because an attacker-influenced kernel OOB pointer write is directly established.
* Applied paranoid manual-review safety floor: 2 -> 5. No additional speculative exploitation points were added.
* Final recommended bucket: **Actionable Moderate / Strong Important candidate requiring manual review**::

2. Signal breakdown

* +2 Strong corruption primitive. The firmware-controlled `clc->idx` selects an entry beyond `phy->clc`, and the assignment can store the kernel pointer returned by `devm_kmemdup()` outside that array. This is a concrete attacker-influenced OOB write, although the value is constrained.
* +1 Reliable DoS. A zero or undersized record length can prevent the record loop from advancing. The invalid reads, oversized copy, and OOB pointer access also plausibly cause a kernel fault or driver failure.
* +1 Firmware-mediated external influence. The malformed CLC data enters through a firmware image rather than through ordinary WiFi traffic.
* -2 Host-admin-equivalent privilege. Deliberately replacing the host firmware image and causing it to be loaded normally requires administrative control of the host firmware store or driver lifecycle.
* No additional Availability point was awarded because the hang, crash, and initialization failure represent the same availability consequence.
* Arbitrary write was not established. The destination is index-selected but relative to `phy->clc`, and the stored value is a kernel-generated allocation pointer.
* Controlled reclaim, callback control, credential corruption, disclosure, and privilege escalation were not demonstrated.
* Remote reachability was not established. Ordinary wireless frames do not directly supply this CLC image.
* Confidentiality and separate integrity-consequence bonuses were withheld because no disclosure path or specific security-sensitive adjacent field is visible.
* No rare-hardware penalty was applied. MT7921 hardware is specialized but not shown to be genuinely rare.
* This is not a repeated-release, refcount, RCU, or UAF case. The related lifetime floors and bonuses do not apply.

Arithmetic for both interpretations:

`+2 strong OOB write +1 DoS +1 firmware mediation -2 host administration = 2`

The final score is raised to 5 by the controlled-corruption manual-review safety floor.

3. Reachability analysis

The vulnerable function parses a CLC firmware blob while initializing or resetting an MT7921 device. A malicious actor must arrange for a malformed image to be available through the kernel firmware-loading path and then cause the driver to load it.

The supplied path does not show an ordinary user, network namespace, delegated capability, or WiFi peer controlling that image. Firmware replacement and driver reload are host-administrative operations under normal Linux firmware-loader semantics. The operation is not namespace-scoped, and no attacker-created namespace provides the complete trigger chain.

A compatible MT7921 device and the affected CLC support are prerequisites. No race is required. Once a malformed image is installed, triggering is deterministic during the relevant firmware load.

4. Primitive and severity interpretation

The primary primitive is an index-selected OOB pointer write from:

`phy->clc[clc->idx] = devm_kmemdup(...)`

Before the write, the same unchecked index also causes an OOB read in the duplicate-initialization check. Other malformed fields can move the region pointer before the firmware buffer, permit an oversized copy, or create a non-advancing loop.

The destination is not arbitrary across kernel memory, and the written pointer value is not freely selected. However, the attacker controls the array index and can potentially target adjacent fields in the active `mt792x_phy` object. This is stronger than validation-only or crash-only behavior and supports CLASS_A, but it does not establish arbitrary kernel read/write or LPE.

The demonstrated practical consequences are driver failure, CPU stall, Oops, or kernel crash. Corruption of adjacent active state is concrete, while privilege escalation remains speculative. ImportantCandidate is YES because the OOB write requires inspection of the structure layout, reachable indexes, zero-value condition, and later consumers. AutoDowngradeAllowed is NO because automatically treating this as an ordinary malformed-firmware DoS would discard a concrete kernel corruption primitive.

Operational severity is limited by the host-admin requirement, but the memory-corruption mechanics warrant actionable manual review.

5. One-sentence report phrase

A malformed MT7921 CLC firmware image can trigger out of bounds reads, a non advancing parser loop, and an index selected kernel pointer write beyond phy clc, requiring host firmware control but warranting manual review for adjacent object corruption.

6. Manual review recommendation

MANUAL CHECK REQUIRED

Review the layout following `phy->clc`, the maximum reachable `clc->idx`, whether target slots can predictably be zero, and how corrupted adjacent fields are subsequently consumed.

7. Call-site confidence

Call-site confidence: medium

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

Patch: wifi: mt76: mt7921: validate CLC firmware records [ Upstream
Commit: 602a950134ee2940136f60797e4457c3983b06ce
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=602a950134ee2940136f60797e4457c3983b06ce

Changed files:
  drivers/net/wireless/mediatek/mt76/mt7921/mcu.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=602a950134ee2940136f60797e4457c3983b06ce

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

The original Linux kernel CVE announcement for CVE-2026-98159 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98159

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:L/I:L/A:H
  The Best / paranoid CVSS vector: AV:L/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H
  The Best / paranoid CVSS score: 6.7

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: 5

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).