[CVE-2026-90408][MODERATE REGULAR] wifi: ath12k: fix overreads in ath12k_wmi_process_csa_switch_count_event() [ Upstream

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

CVE: CVE-2026-90408
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: wifi: ath12k: fix overreads in ath12k_wmi_process_csa_switch_count_event() [ Upstream
Commit: bf97c9d5123859a07848462539153176db029f3a
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=bf97c9d5123859a07848462539153176db029f3a
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90408
Analysis date: Fri, 18 Sep 2026 08:26:24 -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-2026-90408 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90408

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-2026-90408	MODERATE	https://www.kernelcve.org/list/?q=CVE-2026-90408 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:L/I:N/A:H';CWE-125;*CWE-20;CWE-130;Other CVSS 'AV:A/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '5.9';DESCR 'An out-of-bounds read can occur in ath12k_wmi_process_csa_switch_count_event() because the CSA switch count WMI event lacked a TLV policy minimum length and because firmware supplied num_vdevs was used as a loop bound for vdev_ids without checking the actual TLV payload length. A malformed or malicious firmware mediated WMI event can make the driver read past the vdev_ids array while processing CSA switch count status data. For the CVSS the PR:N is selected because no privileges are required on the victim if the event can be induced through the wireless or device side input path. The issue is not Internet remote in the usual TCP/IP sense and is better treated as adjacent or device mediated. Impact is mainly denial of service through invalid kernel reads or a possible crash. A limited confidentiality impact is kept only in the paranoid score because the primitive is an out-of-bounds read in kernel context, but no direct user visible information leak is shown.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline / manual review recommended (with actual score 3)	YES	REMOTE OOB SIMPLEFIX NETWORK HARDWARE LINUS TEST  DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN4	NO	NO	checked

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

ActionableScore=3
ActionableScoreLower=2
PrimitiveClass=CLASS_C
RealUAF=NO
HostAdminRequired=UNKNOWN
NamespaceScopedPrivilege=NO
ImportantCandidate=NO
ManualReview=RECOMMENDED
AutoDowngradeAllowed=YES

1. ActionableScore

* Raw conservative score: 2
* Conservative score: 2. No floor or cap applied.
* Raw paranoid score: 3
* Paranoid score: 3. No floor or cap applied.
* Final recommended bucket: **Borderline / manual review recommended**::

2. Signal breakdown

Conservative signals:

* +1 Weak read-only OOB primitive. The patch establishes that `num_vdevs` from firmware can exceed the actual `vdev_ids` TLV payload length, causing an out-of-bounds read.
* +1 Firmware-mediated external influence. The malformed data comes through a WMI event supplied by firmware, and the Wi-Fi environment may indirectly influence firmware events, but this is not direct Internet or raw packet reachability.

Paranoid additional signal:

* +1 Possible availability impact. The OOB read can plausibly lead to invalid kernel memory access, warning, KASAN report, or driver/kernel crash, although the patch does not demonstrate a reliable panic.

Non-awarded signals:

* RealUAF not awarded. No freed object or stale post-lifetime use is shown.
* CLASS_A not awarded. There is no OOB write, arbitrary write, controlled reclaim, type confusion, callback control, or ownership violation.
* Confidentiality not awarded. The OOB read is internal to kernel/driver processing and no user-visible, network-visible, or device-visible disclosure path is established.
* Integrity not awarded. No unauthorized modification of kernel state or protected data is shown.
* Direct remote reachability not awarded. The input is firmware-mediated, not directly parsed from attacker TCP/IP traffic.
* Strong DoS not awarded conservatively. The patch says OOB read, but does not show a reliable host-wide crash.
* ImportantCandidate not set. The established primitive is limited OOB read without disclosure, write, UAF, or security-boundary bypass.

3. Reachability analysis

The vulnerable path is in `ath12k_wmi_process_csa_switch_count_event()` and processes CSA switch count status data received via ath12k WMI firmware events. The immediate producer of the malformed TLV is firmware, not a local syscall or directly exposed network parser.

A local host administrator is not clearly required to trigger the vulnerable processing once the device and driver are active, but the complete attacker-controlled path is not fully established. A realistic attacker model may involve adjacent wireless influence, malicious or compromised firmware, or device-side fault injection. Therefore `HostAdminRequired=UNKNOWN` rather than YES or NO.

This is not namespace-scoped. No network namespace or namespaced capability is relevant to the complete trigger chain. No prior privileged setup beyond having supported ath12k hardware and driver operation is assumed from the patch, but the hardware and firmware mediation materially affect reachability.

Race repeatability is not relevant. This is a length-validation/input-validation bug, not a timing race.

4. Primitive and severity interpretation

The exact primitive is a read-only out-of-bounds access over the `vdev_ids` array because `num_vdevs` is trusted before being bounded against the TLV payload length. A missing TLV policy entry also allowed the fixed-size event structure minimum length to be unenforced.

This is not an active structured UAF and not fixed stale storage. It is an invalid read from malformed firmware-supplied TLV data. The demonstrated consequence is an OOB read and possible crash or warning. The speculative consequence is limited confidentiality impact if some later undisclosed path reflected the read data, but such a path is not shown and is not scored.

PrimitiveClass is CLASS_C because the behavior is primarily invalid read / DoS-oriented without an independently useful corruption primitive. ImportantCandidate is NO because there is no evidence of memory corruption beyond read-only OOB access, no leak channel, no write primitive, no lifetime violation, and no authorization bypass. AutoDowngradeAllowed is YES because no unresolved Important-grade primitive remains, although manual review is still recommended due to the wireless firmware-mediated input surface.

Likely operational severity is ordinary Moderate to borderline Moderate, depending on whether adjacent wireless attackers can reliably cause malformed CSA-related firmware events.

5. One-sentence report phrase

An out-of-bounds read in ath12k CSA switch count WMI event handling can occur when firmware supplied num_vdevs exceeds the actual vdev_ids TLV payload length, making the issue mainly a firmware-mediated or adjacent-input DoS concern without a demonstrated disclosure or write primitive.

6. Manual review recommendation

MANUAL CHECK RECOMMENDED

Manual review is recommended because this is an OOB read in a wireless driver event path and reachability from adjacent wireless inputs versus only malformed firmware behavior is not fully resolved. It is not marked required because no UAF, OOB write, disclosure channel, privilege escalation, or concrete security-boundary bypass is established.

7. Call-site confidence

Call-site confidence: medium

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

Patch: wifi: ath12k: fix overreads in ath12k_wmi_process_csa_switch_count_event() [ Upstream
Commit: bf97c9d5123859a07848462539153176db029f3a
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=bf97c9d5123859a07848462539153176db029f3a

Changed files:
  drivers/net/wireless/ath/ath12k/wmi.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=bf97c9d5123859a07848462539153176db029f3a

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

The original Linux kernel CVE announcement for CVE-2026-90408 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90408

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:L
  The Best / paranoid CVSS vector: AV:A/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:H
  The Best / paranoid CVSS score: 5.9

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).