[CVE-2026-68195][MODERATE REGULAR] wifi: mt76: mt7615: drop TXRX_NOTIFY on non-mmio buses

[CVE-2026-68195][MODERATE REGULAR] wifi: mt76: mt7615: drop TXRX_NOTIFY on non-mmio buses

[AL-KERNEL]

CVE: CVE-2026-68195
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: wifi: mt76: mt7615: drop TXRX_NOTIFY on non-mmio buses
Commit: f2a72f47c5fb4ba6887e85bbe809d7e5b318d9d5
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=f2a72f47c5fb4ba6887e85bbe809d7e5b318d9d5
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68195
Analysis date: Mon, 10 Aug 2026 15:43:09 -0400
ActionableScore: 3
ActionableScore lower bound: 1
Actionable bucket: Borderline Moderate. Manual review recommended because firmware or adjacent wireless influence may be possible
Manual review required: YES

Summary:
A TXRX_NOTIFY event on mt7615 non MMIO USB or SDIO devices can reach an MMIO-only TX cleanup path and call a NULL tx_cleanup callback, causing a kernel crash through a firmware or device mediated receive path.

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

The original Linux kernel CVE announcement for CVE-2026-68195 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68195

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-2026-68195	MODERATE	CHECK WITH IMPACT FROM ORIG NN LOW	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:A/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H';**CWE-476;CWE-754;CWE-703;Other CVSS 'AV:P/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '5.3';DESCR 'A NULL pointer dereference can occur in the mt76 mt7615 receive path because PKT_TYPE_TXRX_NOTIFY is handled on USB and SDIO devices even though this event is intended for MMIO devices only. On mt7663 USB and SDIO buses the tx_cleanup queue callback is NULL, so dispatching this event into mt7615_mac_tx_free can crash the RX worker and bring down the kernel. For the CVSS the PR:N is used for the paranoid score because the risky input is an event arriving from the device or adjacent wireless environment rather than an operation requiring a local user account. The realistic exposure is limited to systems using affected MediaTek mt76 non MMIO WiFi devices, and practical triggering likely requires a faulty or malicious device, compromised firmware, or a defensible adjacent WiFi based path. Impact is denial of service only via kernel crash.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline Moderate. Manual review recommended because firmware or adjacent wireless influence may be possible (with actual score 2)  SKIP CVE-2026-68195 UNKNOWN SKIP No affected files built, so skip this CVE NO  - - unknown 	MAYBE	REMOTE SIMPLEFIX NETWORK SKB DMAorINTERRUPT HARDWARE  DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5	-	-	checked

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

ActionableScore=3
ActionableScoreLower=1

## 1. ActionableScore

* Conservative score: 1
* Paranoid score: 3
* Final recommended bucket: **Borderline Moderate. Manual review recommended because firmware or adjacent wireless influence may be possible**::

## 2. Signal breakdown

Conservative score:

* Reliable kernel crash / strong DoS: +1. A TXRX_NOTIFY event on non MMIO mt7663 USB or SDIO devices reaches mt7615_mac_tx_free(), which calls a NULL queue_ops->tx_cleanup callback.
* Physical-only or rare hardware-only condition: -2. The clearest trigger requires affected MediaTek mt76 non MMIO hardware or faulty or malicious device behavior.
* Firmware-mediated external influence: +1. The problematic input is an RX side device or firmware event rather than a normal local syscall path.

Conservative total: 1

Paranoid score:

* Firmware-mediated external influence: +1. A compromised or faulty device firmware can plausibly generate the invalid TXRX_NOTIFY event.
* Reliable kernel crash / strong DoS: +1. The NULL callback call is a direct crash condition in the RX worker path.
* Availability impact realistic: +1. If the event is delivered repeatedly or reliably, the impact can be host-visible kernel DoS rather than only a local driver warning.

Paranoid total: 3

Not counted:

* No generic memory corruption. This is a NULL function pointer dereference, not UAF, double free, OOB write, type confusion, or refcount corruption.
* No privilege escalation signal. The patch does not show attacker-controlled callback redirection, reclaim, object replacement, arbitrary write, or stale object reuse.
* No direct remote/network-triggerable signal. A normal WiFi packet path to TXRX_NOTIFY is not demonstrated.

## 3. Reachability analysis

The realistic trigger is a TXRX_NOTIFY event received on mt7663 USB or SDIO devices, where the callback table does not implement tx_cleanup. A local unprivileged user is not clearly able to trigger this directly through a syscall or ordinary socket API. The most defensible attacker models are faulty firmware, compromised firmware, malicious hardware, or a possible but unproven adjacent WiFi influence path.

Namespaces and containers do not materially lower the privilege requirement because the bug is in a device RX worker path, not in a namespaced user API. The affected path is only relevant on systems using the affected MediaTek mt76 non MMIO devices, so exposure is hardware-dependent rather than broad/default kernel exposure.

Call-site confidence: high. The provided patch and commit message explicitly identify the call chain mt7615_rx_check() / mt7615_queue_rx_skb() -> mt7615_mac_tx_free() -> mt76_queue_tx_cleanup() -> queue_ops->tx_cleanup NULL.

## 4. Severity interpretation

This behaves like a hardware or firmware mediated Moderate DoS issue, not an Important-class memory corruption vulnerability. The theoretical concern is that the trigger may originate outside the host CPU through device or wireless influenced input, but the demonstrated primitive is only a NULL pointer dereference. There is no evidence of controlled memory corruption, confidentiality impact, integrity impact, or privilege escalation.

## 5. One-sentence report phrase

A TXRX_NOTIFY event on mt7615 non MMIO USB or SDIO devices can reach an MMIO-only TX cleanup path and call a NULL tx_cleanup callback, causing a kernel crash through a firmware or device mediated receive path.

## 6. Manual review recommendation

MANUAL CHECK RECOMMENDED

Reason: the score is not Important-class, but manual review is justified because this is a kernel crash in a WiFi RX path with possible firmware-mediated or adjacent-device influence.

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

Patch: wifi: mt76: mt7615: drop TXRX_NOTIFY on non-mmio buses
Commit: f2a72f47c5fb4ba6887e85bbe809d7e5b318d9d5
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=f2a72f47c5fb4ba6887e85bbe809d7e5b318d9d5

Commit description:

PKT_TYPE_TXRX_NOTIFY is an mmio-only event, but mt7615_rx_check() and
mt7615_queue_rx_skb() dispatch it to mt7615_mac_tx_free() on every bus.
mt7615_mac_tx_free() cleans the DMA tx queues with
mt76_queue_tx_cleanup(), which calls queue_ops->tx_cleanup(). Only the
mmio queue ops implement that callback; on the mt7663 USB and SDIO
buses it is NULL, so a TXRX_NOTIFY there calls a NULL pointer in the RX
worker. Same defect as the mt7921 and mt7925 patches in this series.

Drop the event on non-mmio buses via mt76_is_mmio(), as in
commit 5683e14 ("wifi: mt76: connac: do not check WED status for
non-mmio devices").

Fixes: eb99cc9 ("mt76: mt7615: introduce mt7663u support")
Cc: stable@vger.kernel.org
Signed-off-by: Devin Wittmayer <lucid_duck@justthetip.ca>
Link: https://patch.msgid.link/20260627191336.20223-4-lucid_duck@justthetip.ca
Signed-off-by: Felix Fietkau <nbd@nbd.name>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  drivers/net/wireless/mediatek/mt76/mt7615/mac.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=f2a72f47c5fb4ba6887e85bbe809d7e5b318d9d5

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

The original Linux kernel CVE announcement for CVE-2026-68195 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68195

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:P/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS vector: AV:A/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS score: 5.3

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: 1
  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).