[CVE-2026-80816][MODERATE 7.0] ALSA: FCP: Use a private URB for the notification endpoint

[CVE-2026-80816][MODERATE 7.0] ALSA: FCP: Use a private URB for the notification endpoint

[AL-KERNEL]

CVE: CVE-2026-80816
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: ALSA: FCP: Use a private URB for the notification endpoint
Commit: 65aceb45ca91ddb7f7ed178821f481b34da35543
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=65aceb45ca91ddb7f7ed178821f481b34da35543
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80816
Analysis date: Fri, 04 Sep 2026 18:23:33 -0400
ActionableScore: 5
ActionableScore lower bound: 3
Actionable bucket: Actionable Moderate at minimum
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-2026-80816 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80816

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-2026-80816	MODERATE	https://www.kernelcve.org/list/?q=CVE-2026-80816 CHECK WITH IMPACT FROM ORIG NN MODERATE	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:L/A:H';CWE-665;**CWE-476;*CWE-416;Other CVSS 'AV:P/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H';BEST CVSS score: '5.7';DESCR 'An ALSA USB FCP initialization bug can occur when the driver shares the mixer status URB instead of using a private FCP notification URB. On a device that exposes the optional UAC2 status interrupt endpoint, fcp_init_notify can return success without submitting the FCP notification URB and cmd_done may remain uninitialized, causing a kernel crash when fcp_init waits for command completion. The same ownership mistake can also make FCP cleanup kill and free the mixer status URB, which is a memory lifetime risk and should be treated as a UAF candidate for manual review. For the CVSS the PR:N because a malicious USB device can trigger the vulnerable path without host privileges if it can be attached to the target system. The issue is not network reachable and normally requires physical USB access or a passed through USB device. Impact is at least denial of service via kernel crash, with limited confidentiality or integrity risk considered in the paranoid score due to possible wrong URB ownership and stale pointer behavior.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 4) 	MAYBE	DANGER USB INIT HARDWARE LINUS  DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5	-	-	checked

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

ActionableScore=5
ActionableScoreLower=3

1. ActionableScore
* Conservative score: 3
* Paranoid score: 5
* Final recommended bucket: **Actionable Moderate at minimum**::

2. Signal breakdown
* Firmware-mediated external influence: +1. A crafted or unusual USB audio device can influence the vulnerable initialization path through endpoint layout and device behavior.
* Memory corruption, Weak/indirect corruption candidate: +1. The bug mixes ownership of mixer->urb and the FCP notification URB, creating a wrong-object lifetime situation rather than a proven controlled overwrite.
* Real lifetime corruption: +1. fcp_cleanup_urb() could kill and free the mixer status URB owned by mixer.c, which is a plausible UAF or double-cleanup candidate.
* Reliable kernel crash / strong DoS: +1. cmd_done can remain zeroed and wait_for_completion_timeout() can crash on an uninitialized wait head.
* Physical-only or rare hardware-only condition: -2. Triggering requires a suitable physical or passed-through USB device, not network access.
* Availability impact realistic: +1 in conservative scoring because the described failure is a concrete kernel crash.
* Paranoid additional concern: +2 total uplift. The wrong URB ownership and stale completion state justify manual-review sensitivity for limited C/I or LPE concern, but not a strong LPE primitive.

3. Reachability analysis
A malicious or malformed USB audio device matching the FCP and optional UAC2 status endpoint conditions is the realistic trigger. No local host privileges are required if the attacker can attach the device physically or through USB passthrough. This is not network reachable. Containers and namespaces generally do not matter unless they control USB passthrough or device assignment. The affected path is device-specific to ALSA USB FCP / Focusrite-style devices, so exposure is narrower than generic USB audio.

4. Severity interpretation
This is stronger than an ordinary low-risk USB crash because it combines a reliable initialization crash with a real object lifetime ownership error. The demonstrated impact is DoS. The theoretical memory-corruption potential is plausible due to freeing an URB owned by another subsystem path, but the patch does not show attacker-controlled reclaim, callback control, arbitrary write, or a reliable LPE path. Therefore the conservative score is borderline manual review, while the paranoid score reaches Actionable Moderate.

5. One-sentence report phrase
An ALSA USB FCP initialization flaw can misuse the mixer status URB as the FCP notification URB, leaving cmd_done uninitialized and potentially freeing an URB owned by mixer.c, allowing a crafted physical or passed-through USB device to crash the kernel with a plausible URB lifetime corruption concern.

6. Manual review recommendation
MANUAL CHECK REQUIRED. The issue is physical-only, but the wrong-object URB ownership and cleanup path make it more than a simple NULL dereference and should be reviewed for UAF or double-free consequences.

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

Patch: ALSA: FCP: Use a private URB for the notification endpoint
Commit: 65aceb45ca91ddb7f7ed178821f481b34da35543
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=65aceb45ca91ddb7f7ed178821f481b34da35543

Commit description:

fcp_init_notify() used mixer->urb, which snd_usb_mixer_status_create()
allocates for the optional UAC2 status interrupt endpoint and mixer.c
kills, resubmits and frees. On a device with that endpoint,
fcp_init_notify()'s "already set up" early return fires on the status
URB and returns success without doing anything. No FCP notification
URB is submitted, and cmd_done is left zeroed because it is
initialised past that early return and nowhere else. fcp_init() then
issues init1_opcode and wait_for_completion_timeout() would crash
adding to the zeroed wait.head. fcp_cleanup_urb() would also kill and
free mixer.c's status URB.

Use a separate URB in fcp_data, and initialise cmd_done in
fcp_init_private() where fcp_data is allocated. fcp_init_notify() is
reached again after suspend via fcp_reinit(), and the URB kill path in
fcp_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.

Fixes: 46757a3 ("ALSA: FCP: Add Focusrite Control Protocol driver")
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/2cad281e6434024ca48a9ecc94fa19d6777e9be7.1786290885.git.g@b4.vu
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  sound/usb/fcp.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=65aceb45ca91ddb7f7ed178821f481b34da35543

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

The original Linux kernel CVE announcement for CVE-2026-80816 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80816

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:R/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS vector: AV:P/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:H
  The Best / paranoid CVSS score: 5.7

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: 3
  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: NO
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).