[CVE-2026-64601][MODERATE 7.0] ALSA: us144mkii: capture_urb_complete: redundant usb_anchor_urb corrupts anchor list on each resubmission

[CVE-2026-64601][MODERATE 7.0] ALSA: us144mkii: capture_urb_complete: redundant usb_anchor_urb corrupts anchor list on each resubmission

[AL-KERNEL]

CVE: CVE-2026-64601
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: ALSA: us144mkii: capture_urb_complete: redundant usb_anchor_urb corrupts anchor list on each resubmission
Commit: 16f14f55141d4c55c3f321f93c328fff7cd6860a
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=16f14f55141d4c55c3f321f93c328fff7cd6860a
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64601
Analysis date: Thu, 06 Aug 2026 04:19:33 -0400
ActionableScore: 5
ActionableScore lower bound: 4
Actionable bucket: Actionable Moderate at minimum
Manual review required: YES

Summary:
A redundant `usb_anchor_urb()` call in the ALSA us144mkii capture completion path corrupts the USB anchor list and URB lifetime state, allowing a local user with access to the affected capture device to trigger a use-after-free during stream stop, suspend, or disconnect, with likely DoS and plausible but unproven LPE risk.

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ABOUT THIS REPORT
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The original Linux kernel CVE announcement for CVE-2026-64601 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64601

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.

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AL-KERNEL CLASSIFICATION RESULT
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CVE-2026-64601	MODERATE	CHECK WITH IMPACT FROM ORIG NN MODERATE	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:N/I:N/A:H';BEST CVSS score: '7';DESCR 'A use-after-free can occur in the ALSA us144mkii USB audio capture path because capture_urb_complete() re anchors an URB on every completion even though the URB was already anchored during initial stream submission. Repeated anchoring corrupts the USB anchor doubly linked list and inflates the URB reference count, so later cleanup through usb_kill_anchored_urbs() during stream stop, suspend, or disconnect may traverse corrupted state and dereference freed memory. For the CVSS the PR:L is used because a local user with access to the ALSA capture device can plausibly start and stop capture streams, while physical disconnect or system suspend may also reach the same cleanup path. The issue is not network reachable and requires local interaction with the affected USB audio device. Impact is at least local denial of service via kernel crash. Because this is a use-after-free from anchor list corruption and reference count imbalance, the paranoid impact treats privilege escalation as plausible and uses CIA:HHH for manual-review sensitivity.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 5)	YES	USB UAF HARDWARE LINUS KPANIC 	YES	NO	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=5
ActionableScoreLower=4

## 1. ActionableScore

* Conservative score: 4
* Paranoid score: 5
* Final recommended bucket: **Actionable Moderate at minimum**

## 2. Signal breakdown

* Local unprivileged trigger: +1. A local user with access to the affected ALSA capture device can plausibly start and stop capture streams.
* Memory corruption, strong corruption primitive: +2. The commit explicitly describes corrupted USB anchor list state leading to use-after-free.
* Real lifetime corruption: +1. The bug involves URB reference count imbalance and stale list membership across resubmission and cleanup.
* Reliable kernel crash / strong DoS: +1. Traversal by `usb_kill_anchored_urbs()` during stop, suspend, or disconnect can hit freed state.
* Weak LPE concern in conservative score: +1. UAF exists, but no attacker-controlled reclaim, callback hijack, or overwrite primitive is demonstrated.
* Stronger LPE concern in paranoid score: +2 instead of +1. The UAF is caused by list corruption plus refcount abuse in kernel USB object lifetime management, so privilege escalation deserves manual-review sensitivity.
* Physical-only or rare hardware-only condition: -2. The issue requires the specific ALSA us144mkii USB audio path and practical access to the affected device.
* Hard race subtraction: 0. This is not primarily a narrow timing race. The corruption accumulates through repeated completion resubmission and is later consumed during cleanup.
* Availability impact realistic: 0 additional. Crash impact is already counted via reliable kernel crash / strong DoS.

Call-site confidence: high. The commit names the resubmission path, the initial anchoring site, and the cleanup consumer `usb_kill_anchored_urbs()`.

## 3. Reachability analysis

The bug is locally reachable through the ALSA USB capture path when the affected Tascam us144mkii device and driver are in use. A local user who can access the capture device may be able to trigger repeated URB completion and later cleanup by starting and stopping capture. Suspend or physical disconnect can also reach the cleanup path, but those conditions may require local physical access or system-level control.

Namespaces and containers do not automatically make this broadly reachable. Device node access and USB device passthrough policy determine whether a containerized or reduced-privilege user can reach the vulnerable path. The path is not network reachable. The affected hardware and driver path are relatively niche, so exposure is narrower than common ALSA or USB core bugs.

## 4. Severity interpretation

This is more than an ordinary Moderate correctness issue because the patch fixes explicit use-after-free caused by anchor list corruption and URB lifetime imbalance. Realistic impact is most likely local kernel crash / DoS on systems using the affected USB audio device. Practical privilege escalation is not demonstrated, but the combination of UAF, list corruption, and refcount imbalance is enough to avoid auto-closing and to require manual review.

The conservative score treats it as a rare-hardware local UAF with likely DoS. The paranoid score raises it to Actionable Moderate because the UAF is in kernel object lifetime management and could theoretically be more exploitable than the crash symptom alone.

## 5. One-sentence report phrase

A redundant `usb_anchor_urb()` call in the ALSA us144mkii capture completion path corrupts the USB anchor list and URB lifetime state, allowing a local user with access to the affected capture device to trigger a use-after-free during stream stop, suspend, or disconnect, with likely DoS and plausible but unproven LPE risk.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED

This is a kernel UAF candidate with list corruption and refcount imbalance. Even though exposure is limited to a specific USB audio device, the bug class should not be auto-closed without review.

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UPSTREAM PATCH SUMMARY
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Patch: ALSA: us144mkii: capture_urb_complete: redundant usb_anchor_urb corrupts anchor list on each resubmission
Commit: 16f14f55141d4c55c3f321f93c328fff7cd6860a
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=16f14f55141d4c55c3f321f93c328fff7cd6860a

Commit description:

In capture_urb_complete(), usb_anchor_urb() is called on every
completion callback, but the URB is already anchored from the
initial submission in tascam_trigger_start(). Each redundant call
corrupts the anchor's doubly-linked list and inflates the URB
refcount. When usb_kill_anchored_urbs() traverses the list during
stream stop / suspend / disconnect, the corrupted list leads to
use-after-free.

Remove the redundant usb_anchor_urb() from the resubmit path.

Cc: stable@vger.kernel.org
Fixes: c1bb0c1 ("ALSA: usb-audio: us144mkii: Implement audio capture and decoding")
Signed-off-by: WenTao Liang <vulab@iscas.ac.cn>
Link: https://patch.msgid.link/20260627042949.61767-1-vulab@iscas.ac.cn
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  sound/usb/usx2y/us144mkii_capture.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=16f14f55141d4c55c3f321f93c328fff7cd6860a

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

The original Linux kernel CVE announcement for CVE-2026-64601 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64601

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:N/I:N/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: 4
  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: YES
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).