[CVE-2026-64483][IMPORTANT] ALSA: firewire: isight: bound the sample count to the packet payload

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

CVE: CVE-2026-64483
Priority: IMPORTANT
AL-KERNEL base severity: IMPORTANT
KPANIC flag: YES
Patch: ALSA: firewire: isight: bound the sample count to the packet payload
Commit: 24423e0a9251d348c3f1fb0bb0e61b879e1e976c
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=24423e0a9251d348c3f1fb0bb0e61b879e1e976c
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64483
Analysis date: Sat, 25 Jul 2026 11:11:08 -0400
ActionableScore: 7
ActionableScore lower bound: 5
Actionable bucket: Strong Important candidate / Actionable Moderate at minimum
Manual review required: YES

Summary:
A malicious or faulty Apple iSight compatible FireWire device can supply an excessive sample_count during normal capture, causing kernel out-of-bounds read and write in the ALSA FireWire iSight driver and potentially leading to crash or memory corruption.

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ABOUT THIS REPORT
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The original Linux kernel CVE announcement for CVE-2026-64483 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64483

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: IMPORTANT
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-2026-64483	IMPORTANT	CHECK WITH IMPACT FROM ORIG NN LOW	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:P/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H';*CWE-787;CWE-125;*CWE-20;Other CVSS 'AV:P/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:H';BEST CVSS score: '6.6';DESCR 'Apple iSight FireWire capture can process a device supplied sample_count that is larger than MAX_FRAMES_PER_PACKET. This allows isight_samples to read beyond the packet payload and write beyond runtime dma_area during normal audio capture, creating a kernel out-of-bounds read and out-of-bounds write condition. For the CVSS the PR:N because the attacker does not need an account on the host, but must control or attach a malicious FireWire iSight compatible device and the victim must start or allow capture. The issue is not network reachable. Impact is at least denial of service via kernel memory corruption and in the paranoid case may include confidentiality and integrity impact or local privilege escalation through kernel memory corruption. FireWire audio devices are usually local peripherals, so real world exposure is limited to systems where such hardware can be connected or already exists.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Strong Important candidate / Actionable Moderate at minimum (with actual score 7)	YES	DMAorINTERRUPT HARDWARE LINUS PACKET  KPANIC INCREASED_TO_MODERATE_FROM_LOW_BASED_ON_GUESSCVSS KPANIC INCREASED_TO_HIGH_BASED_ON_ACTIONABLESCOREHIGHEREQTHAN7	NO	NO	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=7
ActionableScoreLower=5

## 1. ActionableScore

* Conservative score: 5
* Paranoid score: 7
* Final recommended bucket: **Strong Important candidate / Actionable Moderate at minimum**::

## 2. Signal breakdown

Conservative signals:

* Firmware-mediated external influence: +1
  The attacker input comes from a malicious or faulty Apple iSight compatible FireWire device.
* Memory corruption, Strong corruption primitive: +2
  The patch description explicitly states out-of-bounds read past `payload->samples` and out-of-bounds write past `runtime->dma_area`.
* Reliable kernel crash / strong DoS: +1
  Kernel memory corruption during normal capture can realistically crash the host.
* Privileged kernel/device-management memory corruption path: +1
  The corruption occurs in a trusted kernel driver path processing device-supplied isochronous data.
* Physical-only or rare hardware-only condition: -2
  Trigger requires a FireWire Apple iSight compatible device or equivalent malicious hardware on the local bus.
* Confidentiality impact plausible: +1
  OOB read from packet-adjacent memory is present, although disclosure path is not clearly demonstrated.
* Integrity impact plausible: +1
  OOB write into kernel-owned PCM DMA memory is present.

Conservative total: 5

Paranoid additional signal:

* Privilege escalation plausible: +2
  The primitive includes attacker-influenced kernel out-of-bounds write. No exploit chain is demonstrated, but kernel memory corruption in a device-fed capture path is enough for manual-review sensitivity.

Paranoid total: 7

## 3. Reachability analysis

The bug is not network reachable. It is reachable by a malicious or faulty Apple iSight compatible FireWire device during normal audio capture. The attacker does not need a local user account on the host, but physical or bus-level device control is required, and capture must be started or allowed by the victim environment.

Namespaces and containers do not materially lower the trigger requirement because the input source is the physical FireWire device path, not a namespaced local API. The affected subsystem is not broadly exposed on typical servers, and FireWire iSight hardware is relatively rare. However, when present, the vulnerable path is a normal capture path and the malformed `sample_count` is device-controlled.

Call-site confidence: high. The commit message describes the exact call into `isight_samples()` and the precise bounds failure.

## 4. Severity interpretation

This is stronger than an ordinary Moderate because the patch fixes a concrete kernel OOB read and OOB write, not just a warning or validation-only issue. Realistic exploitation is constrained by physical device access and rare hardware exposure, so it is not a broad remote Important issue. The conservative interpretation is Actionable Moderate. The paranoid interpretation is Strong Important candidate because attacker-influenced kernel memory corruption can plausibly exceed DoS even though no LPE exploit path is demonstrated.

## 5. One-sentence report phrase

A malicious or faulty Apple iSight compatible FireWire device can supply an excessive sample_count during normal capture, causing kernel out-of-bounds read and write in the ALSA FireWire iSight driver and potentially leading to crash or memory corruption.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED

Reason: the bug contains an explicit kernel out-of-bounds read and out-of-bounds write primitive controlled by device-supplied packet metadata, so it should not be auto-closed despite the physical-only exposure.

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

Patch: ALSA: firewire: isight: bound the sample count to the packet payload
Commit: 24423e0a9251d348c3f1fb0bb0e61b879e1e976c
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=24423e0a9251d348c3f1fb0bb0e61b879e1e976c

Commit description:

isight_packet() takes the frame count from the device iso packet and
checks it only against the device claimed iso length.

	count = be32_to_cpu(payload->sample_count);
	if (likely(count <= (length - 16) / 4))
		isight_samples(isight, payload->samples, count);

length is the iso header data_length. It can be up to 0xffff. So the
gate allows a count up to about 16379. isight_samples() then copies
count frames out of payload->samples into the PCM DMA buffer.

payload->samples holds only 2 * MAX_FRAMES_PER_PACKET values. The
device multiplexes two samples per frame. A count past
MAX_FRAMES_PER_PACKET reads past the payload. A count past the buffer
size writes past runtime->dma_area. The smallest PCM buffer is larger
than MAX_FRAMES_PER_PACKET. Bounding the count to MAX_FRAMES_PER_PACKET
keeps both the read and the write in range.

A malicious or faulty Apple iSight on the FireWire bus reaches this
during a normal capture.

Add the MAX_FRAMES_PER_PACKET bound to the gate.

Fixes: 3a691b2 ("ALSA: add Apple iSight microphone driver")
Suggested-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Cc: stable@vger.kernel.org
Signed-off-by: Maoyi Xie <maoyixie.tju@gmail.com>
Link: https://patch.msgid.link/178205454729.1900991.7807310178296762772@maoyixie.com
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  sound/firewire/isight.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=24423e0a9251d348c3f1fb0bb0e61b879e1e976c

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

The original Linux kernel CVE announcement for CVE-2026-64483 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64483

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:L/I:L/A:H
  The Best / paranoid CVSS vector: AV:P/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
  The Best / paranoid CVSS score: 6.6

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: 5
  Paranoid ActionableScore: 7

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: IMPORTANT
KPANIC detected for this report: YES
Published priority for this report (same as in Subject): IMPORTANT

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).