[CVE-2026-90371][MODERATE 7.0] wifi: mt76: fix RXDMAD_C buffer recycling race [ Upstream

[CVE-2026-90371][MODERATE 7.0] wifi: mt76: fix RXDMAD_C buffer recycling race [ Upstream

[AL-KERNEL]

CVE: CVE-2026-90371
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: wifi: mt76: fix RXDMAD_C buffer recycling race [ Upstream
Commit: 7ac05ed3a50e511c93f8506e555709a208dfce0a
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=7ac05ed3a50e511c93f8506e555709a208dfce0a
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90371
Analysis date: Fri, 18 Sep 2026 02:29:57 -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-2026-90371 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90371

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-2026-90371	MODERATE	https://www.kernelcve.org/list/?q=CVE-2026-90371 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-362;*CWE-416;*CWE-664;Other CVSS 'AV:A/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '7.5';DESCR 'A buffer recycling race exists in the mt76 RX path because RXDMAD_C buffers come from RRO data queue page pools that are owned by a different NAPI context. Direct page pool recycling from the wrong NAPI context can race the owning NAPI and may corrupt page pool lifetime assumptions for RX buffers. A nearby attacker may be able to influence the vulnerable path by sending wireless traffic to an affected MediaTek mt76 device with WED RRO RXDMAD_C enabled. For the CVSS the PR:N is used because triggering does not require a local account on the target when the affected wireless receive path is reachable over the adjacent network. The realistic impact is denial of service via kernel crash or network device failure. The paranoid impact is raised because a page pool recycling race can plausibly become a use after free or memory corruption condition, even if reliable privilege escalation is not proven from the patch alone.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate / Strong Important candidate requiring manual review (with actual score 5)	YES	REMOTE SIMPLEFIX RACE NETWORK KPANIC MEMORY  KPANIC INCREASED_TO_MODERATE7_BASED_ON_GUESSCVSS	YES	NO	checked

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

ActionableScore=5
ActionableScoreLower=4
PrimitiveClass=CLASS_B
RealUAF=NO
HostAdminRequired=NO
NamespaceScopedPrivilege=NO
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 score.

2. Signal breakdown

Conservative signals:

* +2: CLASS_B active kernel buffer lifetime and ownership race. RXDMAD_C buffers belong to RRO data queue page pools tied to a different NAPI context, but the old code allowed direct page pool recycling from the wrong context.
* +1: firmware or device mediated adjacent network influence. Wireless traffic can plausibly drive the RX path, but NIC, DMA, WED, RRO, and queue behavior materially mediate the trigger.
* +1: realistic DoS concern. A page pool recycling race can plausibly cause kernel crash, allocator or page lifetime inconsistency, or network device failure.
* 0: no race penalty. The patch says race, but does not establish a narrow one shot or externally uncontrollable timing window.
* 0: no hardware rarity penalty. mt76 is hardware specific, but the supplied evidence does not prove rare or physical only access beyond adjacent wireless reachability.

Paranoid additional signal:

* +1: attacker influenced repeatable RX lifetime pressure. A nearby attacker may repeatedly generate RX traffic that exercises the vulnerable recycling path, making unresolved page pool lifetime corruption more actionable than a purely local cleanup fault.

Important non-awarded signals:

* Controlled reclaim not demonstrated.
* Arbitrary write not demonstrated.
* RealUAF is not set to YES because the supplied patch establishes a buffer recycling race and page pool lifetime violation, but not a directly shown post-free dereference.
* Confidentiality and integrity bonuses are not awarded because no disclosure path, arbitrary write, protected object modification, or privilege escalation primitive is established.
* Strong LPE leverage +2 is not awarded because attacker controlled reclaim, callback control, refcount takeover, or directed corruption is not shown.
* Extra Availability is not awarded because the same crash or device failure concern is already counted once.
* Direct AV:N style remote reachability is not used for ActionableScore because the path is adjacent wireless and device mediated, not an ordinary Internet reachable socket path.

3. Reachability analysis

The evaluated attacker is a nearby wireless attacker or peer able to send traffic that reaches an affected MediaTek mt76 device. No local account on the victim is required for this traffic driven model, so HostAdminRequired=NO.

The complete trigger still depends on the affected driver path being active, including WED RRO RXDMAD_C queues and page pools owned by another NAPI context. This is not a namespace scoped privilege scenario, so NamespaceScopedPrivilege=NO.

There is no evidence that host administrator privileges are required to send traffic into the RX path. There is also no evidence that the attacker can directly control page pool internals, reclaim placement, or the exact cross NAPI interleaving. The race appears repeatable under RX load, but the patch does not prove a reliable attacker controlled exploitation sequence.

4. Primitive and severity interpretation

The primitive is an active kernel buffer recycling and page pool ownership race. The stale or unsafe state is not merely passive metadata. It affects RX buffer lifetime handling in a driver data path.

This is best classified as CLASS_B. It is stronger than CLASS_C crash only behavior because the bug involves active page pool recycling across the wrong NAPI ownership boundary. It is not CLASS_A because controlled reclaim, arbitrary write, callback hijack, refcount takeover, or demonstrated privilege escalation is not established.

The demonstrated and strongly supported consequence is availability impact through kernel crash, page pool corruption, or network device failure. The speculative consequence is broader memory corruption or UAF-like behavior if the race causes pages or buffers to be reused or recycled inconsistently. That is enough for manual review, but not enough to score as a proven strong exploitation primitive.

ImportantCandidate=YES because this is a network adjacent active lifetime or ownership bug in RX buffer recycling with unresolved page pool corruption leverage. AutoDowngradeAllowed=NO because automatic closure could miss a meaningful kernel lifetime corruption issue even though full exploitation is not demonstrated.

5. One-sentence report phrase

A race in the mt76 RXDMAD_C receive path can recycle page pool buffers through the wrong NAPI context, allowing adjacent wireless traffic to plausibly trigger page lifetime corruption or a kernel DoS on affected WED RRO configurations.

6. Manual review recommendation

MANUAL CHECK REQUIRED

Reason: the bug is network adjacent and affects page pool buffer lifetime semantics, with plausible UAF or memory corruption implications that are not resolved by the small patch alone.

7. Call-site confidence

Call-site confidence: medium

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

Patch: wifi: mt76: fix RXDMAD_C buffer recycling race [ Upstream
Commit: 7ac05ed3a50e511c93f8506e555709a208dfce0a
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=7ac05ed3a50e511c93f8506e555709a208dfce0a

Changed files:
  drivers/net/wireless/mediatek/mt76/dma.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=7ac05ed3a50e511c93f8506e555709a208dfce0a

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

The original Linux kernel CVE announcement for CVE-2026-90371 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90371

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:H/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: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).