[CVE-2026-97930][MODERATE REGULAR] ALSA: usbusx2y: fix in04_last array size mismatch with in04_buf

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

CVE: CVE-2026-97930
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: ALSA: usbusx2y: fix in04_last array size mismatch with in04_buf
Commit: 229cab526580f82839ae8e4e379753c8cf16952e
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=229cab526580f82839ae8e4e379753c8cf16952e
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-97930
Analysis date: Fri, 25 Sep 2026 07:28:54 -0400
ActionableScore: 0
ActionableScore lower bound: unknown
Actionable bucket: Ordinary Moderate
Manual review required: NO

Summary:
No one-sentence report phrase was found.

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

The original Linux kernel CVE announcement for CVE-2026-97930 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-97930

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: NO

A detailed explanation of the methodology and priority rules is included
at the end of this message.

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

CVE-2026-97930	MODERATE	https://www.kernelcve.org/list/?q=CVE-2026-97930 CHECK WITH IMPACT FROM ORIG NN LOW	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:P/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H';CWE-125;CWE-805;CWE-193;Other CVSS 'AV:P/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '5.2';DESCR 'A size mismatch in the ALSA usbusx2y driver causes i_usx2y_in04_int() to copy 24 bytes from a 21-byte in04_buf allocation during the initial control state snapshot. This results in a 3-byte slab out-of-bounds read that can be detected by KASAN and may cause a warning or kernel crash in hardened or diagnostic configurations. The extra bytes are copied into an internal array and the shown comparison path uses only the first 21 bytes, so there is no demonstrated write primitive or reliable data disclosure path. For the CVSS the PR:N value is used because no authenticated user privileges are required once a compatible physical USB device is attached and handled by the driver. The issue is not network reachable and AV:P is used because triggering depends on a locally attached USB device. Impact is primarily denial of service. A limited confidentiality impact is retained in the paranoid score because the invalid read can consume bytes beyond the source object, but privilege escalation is not supported by the available code.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 0)  SKIP CVE-2026-97930 UNKNOWN SKIP The Fixes patch not applied yet, so unlikely that actual: url YES  NO NO unknown 	MAYBE	USB WARNONLY SIMPLEFIX HARDWARE LINUS  INCREASED_FROM_LOW_BASED_ON_REQUIREMANUALCHECK DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN4	-	-	checked

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

ActionableScore=0
PrimitiveClass=CLASS_C
RealUAF=NO
HostAdminRequired=NO
NamespaceScopedPrivilege=NO
ImportantCandidate=NO
ManualReview=RECOMMENDED
AutoDowngradeAllowed=YES

1. ActionableScore

* Raw conservative score: -1
* Conservative score: 0
* Raw paranoid score: -1
* Paranoid score: 0
* Applied score lower bound: -1 -> 0
* Final recommended bucket: **Ordinary Moderate**::

2. Signal breakdown

* +1 Weak corruption concern. A concrete but bounded 3-byte slab out-of-bounds read occurs during `memcpy()`.
* -2 Physical-only or rare hardware dependency. Reaching the path requires a compatible legacy USB audio device handled by the specialized `usbusx2y` driver.
* No confidentiality point. The extra bytes are copied internally, and no userspace, network, or device-visible disclosure path is established.
* No integrity point. There is no out-of-bounds write, UAF, pointer corruption, or active-object modification.
* No reliable-crash point. The patch establishes an invalid read, but not a production kernel panic. A KASAN warning or panic under diagnostic policy is insufficient to establish realistic strong DoS.
* No memory-layout-invariant point was added because it would duplicate the already counted OOB-read primitive.
* No remote, local-unprivileged software-interface, controlled-reclaim, arbitrary-write, or privilege-escalation signal is established.
* The previous CVSS hint does not add ActionableScore points. Its paranoid C:L and A:H values depend on consequences not demonstrated by the supplied data flow.

3. Reachability analysis

The operation is reached when a compatible physical USB audio device is initialized and its interrupt URB completes. Device attachment normally does not require authenticated host-administrator privileges, so `HostAdminRequired=NO`, but this is physical-device reachability rather than an ordinary local software trigger.

No namespace capability participates in the complete path. There is no network trigger, firmware-compromise requirement, or attacker-accessible syscall shown that independently reaches the copy. The specialized legacy USB hardware is a material prerequisite. No race or timing condition is involved.

4. Primitive and severity interpretation

The exact primitive is a fixed-size 3-byte read beyond a 21-byte slab allocation into a 24-byte internal destination. It is not a UAF, overwrite, repeated release, or active structured-object lifetime violation.

The shown comparison loop consumes only the intended 21 bytes. No path exposing the extra copied bytes is established, and no control-flow or subsequent-write effect is visible. The demonstrated behavior is therefore Class C invalid-read behavior, with possible diagnostic failure but no independently useful exploitation primitive.

`ImportantCandidate=NO` because neither confidentiality disclosure, integrity modification, strong DoS, nor privilege escalation is supported. `AutoDowngradeAllowed=YES` because the issue is a bounded physical-device-dependent read with no unresolved lifetime or security-boundary primitive. Operational severity is Low-like to ordinary Moderate.

5. One-sentence report phrase

A legacy ALSA USB driver reads three bytes beyond a small control buffer during device initialization, but no disclosure, write primitive, reliable production crash, or privilege-escalation path is established.

6. Manual review recommendation

MANUAL CHECK RECOMMENDED

Briefly verify that no ioctl, mmap, control daemon, or other omitted call site exposes the complete historical 24-byte `in04_last` snapshot. If no such path exists, automatic downgrade is appropriate.

7. Call-site confidence

Call-site confidence: medium

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

Patch: ALSA: usbusx2y: fix in04_last array size mismatch with in04_buf
Commit: 229cab526580f82839ae8e4e379753c8cf16952e
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=229cab526580f82839ae8e4e379753c8cf16952e

Commit description:

The in04_last array in struct usx2ydev is declared as char[24], but
in04_buf is allocated as sizeof(struct us428_ctls) which is 21 bytes.
In i_usx2y_in04_int(), when ctl_snapshot_last == -2 (initialization
path):

    memcpy(usx2y->in04_last, usx2y->in04_buf, sizeof(usx2y->in04_last));

This copies 24 bytes from a 21-byte slab allocation, reading 3 bytes
past the end of the source object.

Introduce a USX2Y_IN04_SIZE constant defined as sizeof(struct
us428_ctls) and use it consistently for the in04_last array, the
in04_buf allocation, the URB transfer length, and the comparison loop,
replacing the bare 24 and 21 literals throughout.

Fixes: 1da177e ("Linux-2.6.12-rc2")
Cc: stable@vger.kernel.org
Signed-off-by: Tristan Madani <tristan@talencesecurity.com>
Link: https://patch.msgid.link/20260904205826.4071119-1-tristmd@gmail.com
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  sound/usb/usx2y/usbusx2y.c
  sound/usb/usx2y/usbusx2y.h

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=229cab526580f82839ae8e4e379753c8cf16952e

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

The original Linux kernel CVE announcement for CVE-2026-97930 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-97930

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:L
  The Best / paranoid CVSS vector: AV:P/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H
  The Best / paranoid CVSS score: 5.2

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: 0

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).