[CVE-2026-80815][LOW] ALSA: scarlett2: Use a private URB for the notification endpoint

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

CVE: CVE-2026-80815
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: ALSA: scarlett2: Use a private URB for the notification endpoint
Commit: 013448eb7b0d0b91d6168685dab10e9b41baa825
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=013448eb7b0d0b91d6168685dab10e9b41baa825
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80815
Analysis date: Fri, 04 Sep 2026 16:55:04 -0400
ActionableScore: 2
ActionableScore lower bound: 1
Actionable bucket: Ordinary Moderate / Low-like
Manual review required: YES

Summary:
No one-sentence report phrase was found.

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

The original Linux kernel CVE announcement for CVE-2026-80815 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80815

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: LOW
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-2026-80815	LOW	https://www.kernelcve.org/list/?q=CVE-2026-80815 CHECK WITH IMPACT FROM ORIG NN MODERATE	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H';CWE-665;**CWE-476;CWE-404;Other CVSS 'AV:P/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '5.5';DESCR 'The ALSA scarlett2 mixer path can crash because scarlett2_init_notify reused mixer urb even though that URB is owned by mixer.c for the UAC2 status interrupt endpoint. On devices with that endpoint, the already in use check can return success without submitting a scarlett2 notification URB, leaving cmd_done uninitialized before scarlett2_usb_init waits for a command ACK. This can lead to a NULL pointer dereference or invalid wait queue access and cause a kernel crash. For the CVSS the PR:L is used in the paranoid local scenario because an untrusted local user may be able to trigger reprobe resume or reconnect behavior for an already attached affected USB audio device in some desktop or delegated device environments. The normal exposure is physical device based and not network reachable. Impact is denial of service only, with no supported evidence of information disclosure or privilege escalation.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like (with actual score 2)	YES	DANGER USB INIT NOMEMCHK DMAorINTERRUPT HARDWARE LINUS  DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS_AND_CIANNH DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3	YES	NO	checked

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

ActionableScore=2
ActionableScoreLower=1

1. **ActionableScore**

* Conservative score: 1
* Paranoid score: 2
* Final recommended bucket: **Ordinary Moderate / Low-like**::

2. **Signal breakdown**

* Firmware-mediated external influence: +1. The trigger depends on a USB audio device exposing the relevant UAC2 status interrupt endpoint and scarlett2 notification endpoint behavior.
* Reliable kernel crash / strong DoS: +1. The commit explicitly states that `wait_for_completion_timeout()` can crash when adding to a zeroed `wait.head`.
* Availability impact realistic: +1 in the conservative interpretation only if counting the host crash as high-confidence system-wide DoS. I do not double-count it in the lower score because the reliable crash signal already captures the main impact.
* Physical-only or rare hardware-only condition: -2. The issue is device-specific and requires an affected Focusrite Scarlett2-compatible USB audio device or equivalent endpoint layout.
* Local unprivileged trigger: +1 only in the paranoid score. This applies only if an unprivileged local user can cause reprobe, reconnect, suspend/resume, or similar device lifecycle events for an already attached affected USB device.
* Generic memory corruption: +0. The patch shows an uninitialized completion / invalid wait queue access leading to crash, not UAF, OOB write, double-free, type confusion, arbitrary write, or attacker-controlled reclaim.
* Privilege escalation plausible: +0. No supported LPE primitive is visible.
* Confidentiality impact plausible: +0.
* Integrity impact plausible: +0.

3. **Reachability analysis**

The realistic trigger is physical/peripheral-mediated through an affected USB audio device during probe, initialization, suspend, resume, or cleanup paths. It is not network reachable. In normal server deployments this device class is uncommon, while desktop or audio-production systems may be more exposed. Namespace or container delegation does not materially increase exposure unless the environment gives an untrusted user practical control over USB device lifecycle events. Call-site confidence: high, because the patch and commit message include the relevant initialization, resume, cleanup, and `wait_for_completion_timeout()` consequences.

4. **Severity interpretation**

This behaves like an ordinary Moderate or Low-like kernel DoS rather than an Important-class vulnerability. The crash is concrete, but the exploitation conditions are narrow and tied to physical or local device lifecycle control. Theoretical memory-corruption escalation is not supported by the patch because the failure mode is an invalid wait queue/completion state, not a demonstrated stale object reuse, writable UAF, controlled overwrite, callback hijack, or refcount takeover.

5. **One-sentence report phrase**

An ALSA scarlett2 notification setup bug can leave `cmd_done` uninitialized when the shared mixer URB is already in use, allowing an affected USB audio device lifecycle path to trigger a kernel crash, but the issue is physical or local device dependent and does not show a privilege escalation primitive.

6. **Manual review recommendation**

NO MANUAL CHECK NEEDED.
NO MANUAL CHECK REQUIRED COULD BE AUTOCLOSED.

Reason: the issue is a concrete DoS but not network reachable, not broadly exposed, and does not show UAF/OOB/write/type-confusion or a practical privilege escalation path.

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

Patch: ALSA: scarlett2: Use a private URB for the notification endpoint
Commit: 013448eb7b0d0b91d6168685dab10e9b41baa825
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=013448eb7b0d0b91d6168685dab10e9b41baa825

Commit description:

scarlett2_init_notify() used mixer->urb, which
snd_usb_mixer_status_create() allocates for the UAC2 status interrupt
endpoint and mixer.c manages. On a device with that endpoint, the
"already in use" check fires on the status URB and returns 0 for
success without doing anything. No notification URB is submitted, and
cmd_done is left zeroed because it is initialised past that check and
nowhere else. scarlett2_usb_init() then issues SCARLETT2_USB_INIT_1
and wait_for_completion_timeout() would crash adding to the zeroed
wait.head.

Use a separate URB in scarlett2_data, as done for FCP, and initialise
cmd_done in scarlett2_init_private(). mixer.c was also freeing the URB
in snd_usb_mixer_free() and resubmitting it in
snd_usb_mixer_activate(), so scarlett2 must now do both: add
scarlett2_cleanup_urb(), called from private_free and private_suspend,
and a private_resume callback to re-establish the URB after resume.
scarlett2_init_notify() is reached from there, and the URB kill path
in scarlett2_notify() completes cmd_done, leaving a stale count that
would satisfy the next command's wait before the device ACKs. Use
reinit_completion() to clear it.

Also free the URB if the transfer buffer allocation fails, and both if
usb_submit_urb() fails. Move scarlett2_init_notify() up next to
scarlett2_cleanup_urb() so scarlett2_init_private() can reference it
without a forward declaration.

Fixes: 1b65088 ("ALSA: scarlett2: Implement handling of the ACK notification")
Cc: stable@vger.kernel.org
Assisted-by: Claude:claude-opus-5
Signed-off-by: Geoffrey D. Bennett <g@b4.vu>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Link: https://patch.msgid.link/ffb8ba37d5d605dfdfd8576949d67098651f9349.1786290885.git.g@b4.vu
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  sound/usb/mixer.c
  sound/usb/mixer.h
  sound/usb/mixer_scarlett2.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=013448eb7b0d0b91d6168685dab10e9b41baa825

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

The original Linux kernel CVE announcement for CVE-2026-80815 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80815

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:H
  The Best / paranoid CVSS vector: AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS score: 5.5

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: 1
  Paranoid ActionableScore: 2

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: LOW
KPANIC detected for this report: NO
Published priority for this report (same as in Subject): LOW

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).