[CVE-2026-98428][MODERATE REGULAR] ALSA: usb: 6fire: Avoid embedded URBs [ Upstream

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

CVE: CVE-2026-98428
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: ALSA: usb: 6fire: Avoid embedded URBs [ Upstream
Commit: 3ef9093d83ffecb8e5f6c9d5769a52d39df74f7a
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=3ef9093d83ffecb8e5f6c9d5769a52d39df74f7a
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98428
Analysis date: Thu, 15 Oct 2026 08:54:58 -0400
ActionableScore: 3
ActionableScore lower bound: unknown
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-2026-98428 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98428

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
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CVE-2026-98428	MODERATE	https://www.kernelcve.org/list/?q=CVE-2026-98428 CHECK WITH IMPACT FROM ORIG NN LOW | AEGIS IMPACT MODERATE_KPANIC AEGIS_AS=1 LEGACY=MODERATE RESULT=DIFF (independent Legacy and Aegis differ; FINAL: MODERATE, Aegis: MODERATE_KPANIC)	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H';*CWE-416;CWE-911;*CWE-664;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:H';BEST CVSS score: '7';DESCR 'The ALSA USB 6fire driver embeds reference counted URBs inside PCM, MIDI, and communication runtime objects. An URB can remain referenced or be released asynchronously after the containing runtime object has been destroyed, resulting in a kernel use after free and possible memory corruption. A local process may help trigger the vulnerable lifetime transition by using the affected audio or USB device while disconnect, cleanup, or an error path races with URB completion. For the CVSS the PR:L value is used because practical software triggering requires a local user or process with access to the affected ALSA or USB device. The issue is not network reachable and requires the USB 6fire driver and compatible hardware to be present. Impact is at least a local denial of service via kernel crash and in the worst case may include confidentiality and integrity impact or privilege escalation because the underlying primitive is a kernel use after free. The asynchronous lifetime window makes exploitation complex and configuration dependent. Automated impact decision path. The original SimpleNet classifier selected LOW. The primary LLM estimated paranoid CVSS 7 and the production ActionableScore returned 3 with recommendation Borderline / manual review recommended. The production rules then evaluated CVSS thresholds and ActionableScore thresholds. Recorded rule transitions were CVSS and initial triage stage LOW to MODERATE_KPANIC because the manual review requirement was applied. ActionableScore thresholds stage MODERATE_KPANIC to MODERATE because the ActionableScore threshold rule was applied. The legacy KP specialist has no review artifact for this run. The legacy FD or DH downgrade specialist has no review artifact for this run. Exact triggered rule markers were INCREASED_FROM_LOW_BASED_ON_REQUIREMANUALCHECK and DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN4. The independent weaker Aegis shadow evaluated CVSS 2.6 and ActionableScore 1 with primitive class CLASS_B and manual review RECOMMENDED. Its independently reconciled impact was MODERATE_KPANIC. The models disagreed but the aggregation rules retained the production result. The final reported impact is MODERATE.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline / manual review recommended (with actual score 3)	MAYBE	USB INIT NOMEMCHK ERRORPATH UAF HARDWARE PACKET  INCREASED_FROM_LOW_BASED_ON_REQUIREMANUALCHECK DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN4	-	-	checked

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

ActionableScore=3
PrimitiveClass=CLASS_B
RealUAF=YES
HostAdminRequired=UNKNOWN
NamespaceScopedPrivilege=NO
ImportantCandidate=NO
ManualReview=RECOMMENDED
AutoDowngradeAllowed=YES
RequiresHostUID0=UNKNOWN
AuthorizationDecisionBypass=NO
ProtectedResourceImpact=NONE
B4PendingReview=NO
B4PendingConfirmed=NO

1. ActionableScore

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

2. Signal breakdown

Positive signals:

* +2 Real UAF or active lifetime violation. A refcount-managed embedded URB can outlive its containing communication, MIDI, or PCM runtime allocation and be released asynchronously after that storage has been freed.
* +1 Realistic kernel crash or strong DoS. A late USB-core operation on the freed embedded URB can access or mutate reclaimed slab storage and can plausibly produce an Oops or kernel crash.

Negative signals:

* No negative points. Compatible USB 6fire hardware is required, but the supplied evidence does not sufficiently establish a physical-only attacker model or justify a rare-hardware penalty.
* No timing penalty. Asynchronous ordering is required, but the evidence does not establish that the window is narrow, one-shot, or materially difficult to repeat.

Important non-awarded signals:

* No controlled reclaim, attacker-shaped replacement object, arbitrary write, callback hijack, disclosure, or privilege escalation is demonstrated.
* No structured stale-object leverage point was awarded. The affected URB is structured, but the demonstrated problem is a fixed embedded object involved in asynchronous teardown rather than attacker-controlled object substitution.
* No attacker-influenced lifetime point was awarded because control of the complete submit, teardown, and asynchronous release sequence is unresolved.
* No concrete repeated release/refcount point was awarded. Parent runtime destruction ends the storage lifetime, but the patch does not establish an earlier lifetime-ending release of the exact URB followed by a second release of that same URB.
* Paranoid repeated-refcount leverage was withheld for the same reason.
* No additional Availability point was awarded because it would duplicate the same possible kernel crash.
* Confidentiality and integrity points were not awarded merely from the theoretical possibility that reclaimed memory could be affected.
* Remote reachability is not established.
* B5-R does not apply because no retry-accumulated heap OOB write exists.
* B3-PENDING does not apply because no shared-backing write exists.
* AuthorizationDecisionBypass is NO, so B4-PENDING does not apply.
* REAL UAF FLOOR 4 was not applied because this is a constrained fixed embedded-URB teardown case without established reuse leverage.
* REAL UAF FLOOR 5 was not applied because there is no concrete second release of the same URB, controlled reclaim, or meaningful post-reuse structured processing.

3. Reachability analysis

The vulnerable driver and compatible USB 6fire hardware must be present. A local process with access to the ALSA PCM or MIDI interfaces can exercise URB activity, but the supplied evidence does not prove that such a process can independently force the required disconnect, destruction, initialization failure, or asynchronous release ordering.

Host-admin-equivalent privilege is therefore not positively required, but complete below-host-admin triggering is also not established. HostAdminRequired remains UNKNOWN, and RequiresHostUID0 remains UNKNOWN.

USB device teardown is not an attacker-created user or network namespace operation, so NamespaceScopedPrivilege is NO. No network trigger exists. Prior physical device attachment and driver binding are prerequisites. The asynchronous lifetime ordering may be workload-sensitive, but the patch does not establish a sufficiently hard race to justify a timing penalty.

4. Primitive and severity interpretation

The exact primitive is a kernel UAF caused by embedding a separately refcount-managed URB inside a larger runtime allocation. If the containing runtime is destroyed while USB core still holds an asynchronous URB reference, a later URB release can operate on storage whose containing allocation has already ended.

This is best classified as fixed stale storage with a refcounted structured object, not as controlled active-object replacement. The stale activity occurs around error handling, disconnect, destruction, or asynchronous completion. A kernel fault is plausible, but no useful attacker-controlled primitive beyond the fault is established.

This is an ordinary asynchronous post-teardown UAF, not category B concrete repeated lifetime corruption. The evidence does not show an earlier release that may destroy the exact URB followed by another release of the same dangling URB reference.

PrimitiveClass is CLASS_B because the UAF is concrete. ImportantCandidate is NO because controlled reuse, repeated release, attacker-controlled post-free state, sensitive field consumption, and boundary bypass are absent. AutoDowngradeAllowed is YES because the demonstrated case remains a constrained hardware-specific asynchronous lifetime defect whose practical consequence is primarily crash or DoS.

The likely operational severity is Moderate, with uncertainty around trigger permissions and reproducibility.

5. One-sentence report phrase

The ALSA USB 6fire driver can asynchronously release a refcounted URB after its containing runtime allocation has been destroyed, causing a constrained kernel use after free and possible local denial of service.

6. Manual review recommendation

MANUAL CHECK RECOMMENDED

Confirm the complete PCM changes, disconnect ordering, error unwinding, callback synchronization, and whether an ordinary ALSA user can reliably induce teardown while URB references remain outstanding.

7. Call-site confidence

Call-site confidence: medium

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

Patch: ALSA: usb: 6fire: Avoid embedded URBs [ Upstream
Commit: 3ef9093d83ffecb8e5f6c9d5769a52d39df74f7a
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=3ef9093d83ffecb8e5f6c9d5769a52d39df74f7a

Changed files:
  sound/usb/6fire/comm.c
  sound/usb/6fire/comm.h
  sound/usb/6fire/midi.c
  sound/usb/6fire/midi.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=3ef9093d83ffecb8e5f6c9d5769a52d39df74f7a

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

The original Linux kernel CVE announcement for CVE-2026-98428 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98428

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:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
  The Best / paranoid CVSS score: 7

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: 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).