[CVE-2026-63838][MODERATE REGULAR] ASoC: rsnd: Fix potential out-of-bounds access of component_dais[] [ Upstream

[CVE-2026-63838][MODERATE REGULAR] ASoC: rsnd: Fix potential out-of-bounds access of component_dais[] [ Upstream

[AL-KERNEL]

CVE: CVE-2026-63838
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: ASoC: rsnd: Fix potential out-of-bounds access of component_dais[] [ Upstream
Commit: 9f1daac27ca28e98c8c0e4450de42bb68d547250
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=9f1daac27ca28e98c8c0e4450de42bb68d547250
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-63838
Analysis date: Sun, 19 Jul 2026 11:22:27 -0400
ActionableScore: 3
ActionableScore lower bound: 1
Actionable bucket: Borderline, manual review recommended
Manual review required: YES

Summary:
A missing upper bound in the Renesas rsnd ASoC probe loop can read past `component_dais[]` when no zero terminator is present, potentially causing driver probe failure or kernel crash on systems with malformed platform configuration.

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

The original Linux kernel CVE announcement for CVE-2026-63838 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-63838

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-2026-63838	MODERATE	CHECK WITH IMPACT FROM ORIG NN LOW	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:H/UI:N/S:U/C:L/I:L/A:H';CWE-125;CWE-129;*CWE-20;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '5.2';DESCR 'An out of bounds read can occur in the Renesas rsnd ASoC probe path because the loop over priv component_dais used the array value as the only terminator and did not enforce a maximum index. If all valid component_dais entries are populated and the last slot is not zero, the next loop test can read component_dais at index RSND_MAX_COMPONENT outside the array during driver probe. For the CVSS the PR:H means an attacker normally needs administrative control over platform firmware, device tree data, or driver binding conditions needed to reach this malformed probe state. The issue is not network reachable. Impact is mainly denial of service or driver probe failure, with limited additional risk from an invalid kernel read and follow on use of an out of bounds derived component count.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline, manual review recommended (with actual score 2)  SKIP CVE-2026-63838 UNKNOWN SKIP No affected files built, so skip this CVE NO  - - unknown 	MAYBE	KASAN OOB SIMPLEFIX HARDWARE  DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS_AND_CIANNH	-	-	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=3
ActionableScoreLower=1

## 1. ActionableScore

* Conservative score: 1
* Paranoid score: 3
* Final recommended bucket: **Borderline, manual review recommended**::

## 2. Signal breakdown

Conservative signals:

* Firmware-mediated external influence: +1. The malformed state likely depends on device tree, firmware, or platform configuration populating `component_dais[]` without a zero terminator.
* Availability impact realistic: +1. The out-of-bounds access occurs during driver probe and may cause probe failure or kernel fault on affected systems.
* Requires admin/root/platform control in typical deployments: -2. A normal local user usually cannot alter the relevant device tree or platform data.
* Net conservative result is effectively low, rounded to ActionableScoreLower=1 because the bug is still an OOB access in kernel probe code.

Paranoid additional signals:

* Memory corruption, weak/indirect corruption candidate: +1. This is an unchecked array index / missing upper bound, but the shown primitive is read-oriented and not an OOB write.
* Privileged kernel/device-management corruption path: +1. The bug is in trusted driver initialization and uses firmware/platform-derived configuration to drive component registration.
* Reliable kernel crash / strong DoS concern: +1. If the out-of-bounds value is nonzero, the loop may continue and use an invalid `nr` value in follow-on component registration logic.
* Rare/configuration-dependent exposure is not heavily penalized in the paranoid score because affected Renesas rsnd systems may hit this path automatically during normal boot/probe.

No strong LPE signal is awarded. No strong generic memory corruption signal is awarded. No confidentiality signal is awarded because there is no demonstrated user-visible disclosure path.

## 3. Reachability analysis

The most realistic trigger requires control over platform firmware, device tree data, or driver binding conditions that influence `rsnd_dai_of_node()` and the resulting `component_dais[]` contents. This is not network reachable and is not a normal unprivileged local syscall or device API trigger. Namespaces and containers do not materially lower the privilege requirement because the affected state is established during hardware driver probing, not by per-container runtime configuration.

The path is only relevant on systems using the Renesas rsnd ASoC driver with the affected multi-component configuration. On such systems it may be reached during normal driver probe, but attacker control is usually weak unless the attacker can modify firmware or boot-time hardware description.

Call-site confidence: medium. The changed loop and immediate use of `nr = priv->component_dais[i]` are visible, but deeper consequences inside `devm_snd_soc_register_component()` are not shown in the provided patch.

## 4. Severity interpretation

This behaves more like a low-to-borderline Moderate kernel driver robustness issue than an Important vulnerability. The theoretical concern is an out-of-bounds read followed by use of an out-of-bounds-derived component count during driver probe. The realistic evidence supports driver probe failure or kernel crash more than privilege escalation.

The paranoid score keeps it in manual-review territory because OOB access in kernel driver initialization can sometimes hide secondary effects, but the patch does not show attacker-controlled overwrite, reclaim, type confusion, callback control, arbitrary write, or a practical LPE path.

## 5. One-sentence report phrase

A missing upper bound in the Renesas rsnd ASoC probe loop can read past `component_dais[]` when no zero terminator is present, potentially causing driver probe failure or kernel crash on systems with malformed platform configuration.

## 6. Manual review recommendation

MANUAL CHECK RECOMMENDED

Manual review is recommended because this is an OOB kernel access in a driver probe path with firmware/platform influence, but it should not be treated as an Important candidate without additional evidence of a write primitive, sensitive disclosure, or practical privilege escalation.

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

Patch: ASoC: rsnd: Fix potential out-of-bounds access of component_dais[] [ Upstream
Commit: 9f1daac27ca28e98c8c0e4450de42bb68d547250
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=9f1daac27ca28e98c8c0e4450de42bb68d547250

Changed files:
  sound/soc/sh/rcar/core.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=9f1daac27ca28e98c8c0e4450de42bb68d547250

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

The original Linux kernel CVE announcement for CVE-2026-63838 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-63838

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:H/UI:N/S:U/C:N/I:N/A:L
  The Best / paranoid CVSS vector: AV:L/AC:H/PR:H/UI:N/S:U/C:L/I:L/A:H
  The Best / paranoid CVSS score: 5.2

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: 1
  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).