[CVE-2026-90369][MODERATE 7.0] wifi: mt76: fix out-of-bounds access in mmio copy helpers [ Upstream

[CVE-2026-90369][MODERATE 7.0] wifi: mt76: fix out-of-bounds access in mmio copy helpers [ Upstream

[AL-KERNEL]

CVE: CVE-2026-90369
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: wifi: mt76: fix out-of-bounds access in mmio copy helpers [ Upstream
Commit: 6ed0fba58bb125a8d8de96e391aa86111166efca
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=6ed0fba58bb125a8d8de96e391aa86111166efca
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90369
Analysis date: Fri, 18 Sep 2026 05:12:41 -0400
ActionableScore: 5
ActionableScore lower bound: 4
Actionable bucket: Actionable Moderate / Strong Important candidate requiring manual review
Manual review required: YES

Summary:
No one-sentence report phrase was found.

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

The original Linux kernel CVE announcement for CVE-2026-90369 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90369

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.

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

CVE-2026-90369	MODERATE	https://www.kernelcve.org/list/?q=CVE-2026-90369 CHECK WITH IMPACT FROM ORIG NN MODERATE	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:A/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H';*CWE-787;CWE-125;CWE-119;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:H';BEST CVSS score: '7.5';DESCR 'An out-of-bounds access exists in the mt76 MMIO copy helpers because the old loop rounded len up to a 4 byte boundary. For write_copy this can read 1 to 3 bytes past the source buffer and send adjacent kernel data to device registers. For read_copy this can write 1 to 3 bytes past the destination buffer with data read from MMIO, which is a kernel memory corruption primitive. For the CVSS the PR:N is used in the paranoid score because a Wi-Fi adjacent attacker may not need local privileges if an untrusted radio or firmware controlled path can drive an odd length MMIO copy. The issue is not a normal Internet remote bug. Practical exposure is more likely adjacent Wi-Fi or device mediated and must be confirmed by call site review. Impact is at least denial of service via kernel crash and in worst case may allow confidentiality or integrity impact due to memory corruption.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate / Strong Important candidate requiring manual review (with actual score 5)	YES	REMOTE OOB SIMPLEFIX NETWORK KPANIC  KPANIC INCREASED_TO_MODERATE7_BASED_ON_GUESSCVSS	YES	NO	checked

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

ActionableScore=5
ActionableScoreLower=4
PrimitiveClass=CLASS_B
RealUAF=NO
HostAdminRequired=UNKNOWN
NamespaceScopedPrivilege=UNKNOWN
ImportantCandidate=YES
ManualReview=REQUIRED
AutoDowngradeAllowed=NO

1. ActionableScore

* Raw conservative score: 4
* Conservative score: 4
* Raw paranoid score: 5
* Paranoid score: 5
* Final recommended bucket: **Actionable Moderate / Strong Important candidate requiring manual review**::

No floor or cap changed the conservative score. No floor or cap changed the paranoid score.

2. Signal breakdown

Conservative signals:

* +1 Constrained kernel buffer overwrite. `mt76_mmio_read_copy()` can write 1 to 3 bytes past the destination buffer when `len` is not 4 byte aligned.
* +1 Limited OOB read / weak corruption concern. `mt76_mmio_write_copy()` can read 1 to 3 bytes past the source buffer and write the resulting 32 bit value to MMIO, but no user visible disclosure path is established.
* +1 Memory layout invariant violation. The old loop used `ALIGN(len, 4)` for memory access size while the caller supplied buffer length remained `len`.
* +1 Realistic kernel crash / DoS. The read helper has a concrete kernel out of bounds write, which can plausibly corrupt adjacent kernel memory and crash the system.

Paranoid additional signal:

* +1 Firmware-mediated or adjacent-device influence. This is a Wi-Fi MMIO helper, and if an odd length path is reachable through device, firmware, or radio influenced state, the corruption may be reachable without local host privileges. This is not scored as direct Internet remote reachability.

Important non-awarded signals:

* +0 RealUAF. No use-after-free or stale lifetime object is shown.
* +0 Controlled reclaim. No controlled replacement, heap shaping, or object substitution is demonstrated.
* +0 Arbitrary or directed write. The overwrite is limited to the tail of the destination buffer and the payload comes from MMIO data.
* +0 Direct remote network trigger. The patch does not prove that ordinary network traffic directly reaches these helpers.
* +0 Confidentiality. The OOB read is not shown to be returned to userspace or to a remote attacker.
* +0 Integrity beyond corruption primitive. Kernel memory corruption exists, but no specific protected object or security state overwrite is established.
* +0 Weak LPE. Not awarded separately because no concrete privilege-escalation leverage is shown.
* +0 Extra availability. Not added because the same possible crash is already counted once.
* Repeated release/refcount check: no first release, no surviving exact dangling reference, no second lifetime mutation, no repeated-release signal, no Floor 5 from repeated release.

3. Reachability analysis

The vulnerable code is in Mediatek mt76 Wi-Fi MMIO copy helpers. The patch proves the primitive inside the helpers, but the supplied context does not show all call sites or which attacker-controlled inputs can influence `len`, source buffer, destination buffer, or MMIO contents.

Host administrator requirement is therefore UNKNOWN. It is not proven that host root or host CAP_NET_ADMIN is required for the complete trigger, but it is also not proven that an ordinary local user or adjacent Wi-Fi attacker can drive the complete path.

NamespaceScopedPrivilege is UNKNOWN. No complete namespace-scoped trigger chain is supplied.

Prior setup likely includes affected mt76 hardware and the driver being active, but this is not enough to apply a rare-hardware penalty. mt76 devices are real deployed Wi-Fi hardware, and the code is not merely dead or diagnostic.

No race is involved. Attack complexity depends on call-site reachability and whether a non 4 byte aligned length can be induced in practice.

4. Primitive and severity interpretation

The exact primitive is an out-of-bounds memory access caused by iterating to `ALIGN(len, 4)` while using buffers sized for `len`.

The stronger side is `mt76_mmio_read_copy()`, because it performs a 4 byte MMIO read and stores it through `put_unaligned_le32()` into `data + i`, which writes past the destination buffer for a 1 to 3 byte tail. This is a concrete kernel OOB write, but constrained because the overwrite size is small, the target is adjacent to the provided destination buffer, and the payload is MMIO-derived rather than demonstrated attacker-chosen data.

`mt76_mmio_write_copy()` is a concrete OOB read from the source buffer, but no disclosure path to the attacker is established. The bytes are written to device registers, so this is a weaker confidentiality signal unless call-site review shows attacker-observable device behavior.

PrimitiveClass is CLASS_B. The bug is real kernel memory corruption, but not CLASS_A because controlled target selection, arbitrary write, controlled reclaim, callback influence, demonstrated LPE, or concrete security-boundary bypass is not established.

Demonstrated consequence is out-of-bounds access. Practical consequence is likely DoS or memory corruption. Speculative consequence is stronger exploitation if call-site review shows attacker control over length, buffer placement, MMIO value, or repeated reachable invocations.

ImportantCandidate is YES because a concrete kernel OOB write exists in a Wi-Fi driver helper and the exploitation leverage is unresolved. AutoDowngradeAllowed is NO because automatically closing this as ordinary Moderate could lose a real kernel memory corruption primitive that requires call-site review.

Likely operational severity is Actionable Moderate at minimum, with Important review warranted if the helper is reachable from untrusted Wi-Fi, firmware-controlled, or local unprivileged paths.

5. One-sentence report phrase

A non 4 byte aligned length in mt76 MMIO copy helpers can cause a 1 to 3 byte OOB read in the write path or a 1 to 3 byte kernel OOB write in the read path, making this a constrained but real kernel memory corruption issue that requires call-site review.

6. Manual review recommendation

MANUAL CHECK REQUIRED

Reason: the patch establishes a concrete kernel OOB write primitive, but the supplied context does not resolve whether attacker-controlled Wi-Fi, firmware, or local inputs can drive odd lengths and useful buffer placement.

7. Call-site confidence

Call-site confidence: medium

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

Patch: wifi: mt76: fix out-of-bounds access in mmio copy helpers [ Upstream
Commit: 6ed0fba58bb125a8d8de96e391aa86111166efca
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=6ed0fba58bb125a8d8de96e391aa86111166efca

Changed files:
  drivers/net/wireless/mediatek/mt76/mmio.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=6ed0fba58bb125a8d8de96e391aa86111166efca

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

The original Linux kernel CVE announcement for CVE-2026-90369 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90369

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:H/PR:L/UI:N/S:U/C:L/I:L/A:H
  The Best / paranoid CVSS vector: AV:A/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
  The Best / paranoid CVSS score: 7.5

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: 4
  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).