[CVE-2026-64478][MODERATE REGULAR] ALSA: usb-audio: avoid kobject path lookup in DualSense match

[CVE-2026-64478][MODERATE REGULAR] ALSA: usb-audio: avoid kobject path lookup in DualSense match

[AL-KERNEL]

CVE: CVE-2026-64478
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: ALSA: usb-audio: avoid kobject path lookup in DualSense match
Commit: e4c66a149c408e44e60bfec3fabf08b6b7abbc60
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=e4c66a149c408e44e60bfec3fabf08b6b7abbc60
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64478
Analysis date: Sat, 25 Jul 2026 08:49:16 -0400
ActionableScore: 3
ActionableScore lower bound: 2
Actionable bucket: Borderline Ordinary Moderate / manual review recommended
Manual review required: YES

Summary:
A race in the ALSA USB audio DualSense input handler can dereference an invalid kobject name during rapid USB disconnect and reconnect, allowing a physical or USB-emulation attacker to crash the kernel but not showing a clear privilege escalation primitive.

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

The original Linux kernel CVE announcement for CVE-2026-64478 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64478

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-2026-64478	MODERATE	CHECK WITH IMPACT FROM ORIG NN MODERATE	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:P/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:H';CWE-362;*CWE-416;**CWE-476;Other CVSS 'AV:P/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '5.3';DESCR 'A race in the ALSA usb audio DualSense input handler can occur during rapid USB disconnect and reconnect. The match routine builds kobject path strings and kobject_get_path can walk ancestor kobjects while the USB device hierarchy is being torn down, so an invalid kobject name can be dereferenced in strlen and crash the kernel. For the CVSS the PR:N is used for the paranoid score because a physical attacker or malicious USB device emulator can trigger repeated hotplug without a local user account on the target. The issue is not network reachable and requires physical or equivalent USB device access. Impact is at least denial of service via kernel crash. A limited C/I impact is kept only in the paranoid score because the fault is an invalid or stale kobject name dereference during teardown, but there is no clear write primitive.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline Ordinary Moderate / manual review recommended (with actual score 3)	YES	USB INIT HARDWARE LINUS  DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5	YES	NO	checked

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

ActionableScore=3
ActionableScoreLower=2

## 1. ActionableScore

* Conservative score: 2
* Paranoid score: 3
* Final recommended bucket: **Borderline Ordinary Moderate / manual review recommended**::

## 2. Signal breakdown

Conservative signals:

* Weak or indirect corruption candidate: +1
  `kobject_get_path()` may dereference a stale or invalid kobject name during USB teardown. This is closer to stale pointer dereference than a pure logic bug, but no write primitive is shown.

* Real lifetime corruption: +1
  The failure happens because object lifetime and disconnect teardown can race with path lookup.

* Reliable kernel crash / strong DoS: +1
  The commit shows a concrete fault in `strlen()` with a kernel call trace.

* Device-mediated external influence: +1
  A malicious or unstable USB device, or USB device emulation, could plausibly influence hotplug timing.

* Hard or unreliable race / special timing required: -1
  Triggering depends on rapid disconnect/reconnect during registration and teardown.

* Physical-only or rare hardware-only condition: -2
  The realistic attacker model requires physical USB access or equivalent USB emulation.

* Availability impact realistic: +1
  The observed impact is a kernel crash, but this is not double-counted as persistent storage or filesystem corruption.

Paranoid-only signal:

* Broader workstation exposure consideration: +1
  USB audio, HID, and game controller hotplug paths are common on desktop systems, even though the specific DualSense quirk is device-specific.

## 3. Reachability analysis

The bug is not network reachable. It is reachable through physical USB hotplug or equivalent USB device emulation involving a Sony DualSense-compatible device. No local Linux account is required if the attacker has physical access, but exploitation still requires timing a disconnect/reconnect race during device probing. Namespaces and containers do not materially lower the barrier because the trigger is hardware hotplug rather than a normal unprivileged syscall API. The affected path is not a server-default remote exposure, but it can be relevant on desktops, gaming systems, test machines, or hosts where USB passthrough or emulated USB devices are available.

Call-site confidence: high. The provided patch includes the vulnerable function and the commit message provides the concrete call trace.

## 4. Severity interpretation

This behaves more like an ordinary Moderate or physical DoS issue than an Important-class kernel vulnerability. Theoretical memory-lifetime concern exists because the crash comes from dereferencing kobject state while the USB hierarchy is being torn down. Realistic exploitation evidence supports kernel crash only. There is no demonstrated attacker-controlled reclaim, write-after-free, callback control, object replacement, information disclosure path, or privilege escalation primitive.

## 5. One-sentence report phrase

A race in the ALSA USB audio DualSense input handler can dereference an invalid kobject name during rapid USB disconnect and reconnect, allowing a physical or USB-emulation attacker to crash the kernel but not showing a clear privilege escalation primitive.

## 6. Manual review recommendation

MANUAL CHECK RECOMMENDED

Manual review is recommended because this is a teardown race with a stale kobject dereference, but the actionable priority is limited by physical-only reachability, hard timing, and lack of a demonstrated confidentiality, integrity, or LPE primitive.

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

Patch: ALSA: usb-audio: avoid kobject path lookup in DualSense match
Commit: e4c66a149c408e44e60bfec3fabf08b6b7abbc60
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=e4c66a149c408e44e60bfec3fabf08b6b7abbc60

Commit description:

The DualSense jack-detection input handler verifies that a matching input
device belongs to the same physical controller by building kobject path
strings for both the input device and the USB audio device, then comparing
the path prefix.

This was observed when a weak physical connection caused the controller
to rapidly disconnect and reconnect. During that repeated hotplug,
snd_dualsense_ih_match() can run while the controller's USB device is
being disconnected. kobject_get_path() walks ancestor kobjects and
dereferences their names; if the USB device kobject name is no longer
valid, this can fault in strlen():

  RIP: 0010:strlen+0x10/0x30
  Call Trace:
   kobject_get_path+0x34/0x150
   snd_dualsense_ih_match+0x49/0xd0 [snd_usb_audio]
   input_register_device+0x566/0x6a0
   ps_probe+0xb89/0x1590 [hid_playstation]

The same ownership check can be done without building kobject path
strings. The input device is parented below the HID device, USB interface
and USB device, so walking the input device parent chain and comparing
against the mixer USB device preserves the check without dereferencing
kobject names during disconnect.

Fixes: 79d561c ("ALSA: usb-audio: Add mixer quirk for Sony DualSense PS5")
Cc: <stable@vger.kernel.org>
Assisted-by: Cute:gpt-5.5
Signed-off-by: Darvell Long <contact@darvell.me>
Link: https://patch.msgid.link/20260624143723.2986353-1-contact@darvell.me
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  sound/usb/mixer_quirks.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=e4c66a149c408e44e60bfec3fabf08b6b7abbc60

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

The original Linux kernel CVE announcement for CVE-2026-64478 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64478

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:H/PR:N/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS vector: AV:P/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:H
  The Best / paranoid CVSS score: 5.3

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: 2
  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).