[CVE-2026-46184][LOW] sound: ua101: fix division by zero at probe

[CVE-2026-46184][LOW] sound: ua101: fix division by zero at probe

[AL-KERNEL]

CVE: CVE-2026-46184
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: sound: ua101: fix division by zero at probe
Commit: 6162e8212e88c39492d981b248b5e37002486c66
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=6162e8212e88c39492d981b248b5e37002486c66
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46184
Analysis date: Thu, 28 May 2026 10:28:43 -0400
ActionableScore: 0
ActionableScore lower bound: unknown
Actionable bucket: Ordinary Moderate / Low-like
Manual review required: NO

Summary:
A malformed UA-101 USB audio device can report zero channels, causing `frame_bytes` to become zero and later triggering a division-by-zero kernel crash in URB completion handlers.

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

The original Linux kernel CVE announcement for CVE-2026-46184 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46184

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: NO

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-2026-46184	LOW	CHECK	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:P/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H';CWE-369;*CWE-20;CWE-754;BEST CVSS score: '4.6';DESCR 'The ua101 USB audio driver trusted bNrChannels from a class specific USB descriptor and could calculate frame_bytes as zero when a malformed device reported zero channels. Later URB completion handlers use frame_bytes as a divisor, which can trigger a division by zero and crash the kernel. For the CVSS the PR:N is used because the attacker only needs to present a malformed USB device, but the attack vector is physical device attachment rather than a network path. Impact is availability only. There is no supported memory corruption, information disclosure, or privilege escalation primitive.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like (with actual score 0) 	MAYBE	DANGER USB SIMPLEFIX ERRORPATH HARDWARE LINUS  DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5 DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3	-	-	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=0

## 1. ActionableScore

* Conservative score: 0
* Paranoid score: 0
* Final recommended bucket: **Ordinary Moderate / Low-like**::

## 2. Signal breakdown

Positive signals:

* Reliable kernel crash / strong DoS: +1. A malformed UA-101 USB audio device with `bNrChannels = 0` can make `frame_bytes` zero and later trigger division by zero in URB completion.
* Availability impact realistic: +1. Kernel crash is the supported impact.

Negative / limiting signals:

* Physical-only condition: -2. The attacker must present a malformed physical USB device or equivalent USB passthrough device.
* Rare device-specific driver path: -1. The issue affects the Edirol UA-101 USB audio driver, not a broad USB audio core path.
* No memory corruption, information disclosure, integrity impact, or privilege escalation.

Effective triage score is floored at 0.

## 3. Reachability analysis

The practical trigger is attaching or passing through a malformed USB device that reports zero channels in class-specific descriptors. A local user normally needs physical access or control over USB passthrough. The issue is not remotely network reachable.

Containers and VMs matter only if untrusted USB passthrough is allowed. In that case, the guest kernel may be crashed by the malformed device, but the primitive remains availability-only.

## 4. Severity interpretation

This behaves like Low / ordinary Moderate. It is a device-specific physical DoS caused by missing descriptor validation.

There is no evidence of memory corruption, information disclosure, or privilege escalation. The theoretical impact does not extend beyond kernel crash based on the patch.

## 5. One-sentence report phrase

A malformed UA-101 USB audio device can report zero channels, causing `frame_bytes` to become zero and later triggering a division-by-zero kernel crash in URB completion handlers.

## 6. Manual review recommendation

NO MANUAL CHECK NEEDED

This is physical-device availability-only DoS in a specific USB audio driver, with no memory corruption or LPE evidence.

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

Patch: sound: ua101: fix division by zero at probe
Commit: 6162e8212e88c39492d981b248b5e37002486c66
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=6162e8212e88c39492d981b248b5e37002486c66

Commit description:

Add a missing sanity check for bNrChannels in detect_usb_format()
to prevent a division by zero in playback_urb_complete() and
capture_urb_complete().

USB core does not validate class-specific descriptor fields such
as bNrChannels, so drivers must verify them before use. If a
device provides bNrChannels = 0, frame_bytes becomes zero and is
later used as a divisor in the URB completion handlers, leading
to a kernel crash.

Fixes: 63978ab ("sound: add Edirol UA-101 support")
Cc: stable@vger.kernel.org
Signed-off-by: SeungJu Cheon <suunj1331@gmail.com>
Link: https://patch.msgid.link/20260426111239.103296-1-suunj1331@gmail.com
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  sound/usb/misc/ua101.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=6162e8212e88c39492d981b248b5e37002486c66

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

The original Linux kernel CVE announcement for CVE-2026-46184 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46184

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: Not available
  The Best / paranoid CVSS vector: AV:P/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS score: 4.6

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: 0

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).