[CVE-2026-46230][MODERATE 7.0] drm/amdgpu/vcn3: Prevent OOB reads when parsing dec msg

[CVE-2026-46230][MODERATE 7.0] drm/amdgpu/vcn3: Prevent OOB reads when parsing dec msg

[AL-KERNEL]

CVE: CVE-2026-46230
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: drm/amdgpu/vcn3: Prevent OOB reads when parsing dec msg
Commit: 638d3e0b9eb77aa53fdd60e2b928761d16ba76fa
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=638d3e0b9eb77aa53fdd60e2b928761d16ba76fa
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46230
Analysis date: Sat, 01 Aug 2026 09:41:32 -0400
ActionableScore: 5
ActionableScore lower bound: unknown
Actionable bucket: Actionable Moderate at minimum
Manual review required: YES

Summary:
A local user with access to the amdgpu DRM interface can submit a malformed VCN3 decode message that causes out-of-bounds reads during BO-backed message parsing, potentially leading to kernel crash and limited confidentiality concern without evidence of direct privilege escalation.

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

The original Linux kernel CVE announcement for CVE-2026-46230 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46230

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-2026-46230	MODERATE	CHECK WITH IMPACT FROM ORIG NN LOW	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H';CWE-125;*CWE-20;CWE-754;Other CVSS 'AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:H';BEST CVSS score: '7.1';DESCR 'An out of bounds read in the AMDGPU VCN3 decode message parser can occur because vcn_v3_0_dec_msg did not consistently validate message length, buffer count, and per buffer offset and size against the end of the backing BO. A local user with access to the amdgpu DRM device can submit a malformed VCN decode message that makes the kernel read outside the intended BO range while parsing message entries or the create buffer header. For the CVSS the PR:L is used because triggering requires a local process that can access the GPU driver interface, which is commonly exposed through DRM render nodes but still requires local execution on the target. The issue is not network reachable and is triggered through the local graphics command submission path rather than remote traffic. Impact is at least local denial of service via kernel fault or crash, with possible confidentiality impact from an out of bounds read, but no clear evidence of an out of bounds write or privilege escalation primitive in the patch context.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 5)  SKIP CVE-2026-46230  SKIP No affected files built, so skip this CVE NO  - - unknown 	MAYBE	OOB SIMPLEFIX HARDWARE KPANIC 	-	-	checked

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

ActionableScore=5

## 1. ActionableScore

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

## 2. Signal breakdown

Triggered signals:

* Local unprivileged trigger: +1
  A local process with access to the amdgpu DRM device or render node can submit malformed VCN decode command data.

* Reliable kernel crash / strong DoS: +1
  The bug is an out-of-bounds read in kernel-side parsing of BO-backed VCN messages. Invalid bounds can plausibly cause kernel fault or crash.

* Confidentiality impact plausible: +1
  The primitive is read-side OOB access. No direct disclosure path is shown, but OOB read in kernel parsing makes limited confidentiality concern defensible.

* Broad/default/common subsystem exposure: +1
  amdgpu DRM render interfaces are commonly exposed on systems with supported AMD GPUs. This is not a debug-only or exotic kernel path.

* Availability impact realistic: +1
  A malformed command submission can plausibly trigger repeatable system-impacting failure on affected hardware.

Not counted:

* Remote reachable: +0
  No network path is involved.

* Strong memory corruption: +0
  Patch shows OOB reads, not OOB write, UAF, double-free, arbitrary write, or type confusion.

* Privilege escalation plausible: +0
  No reclaim, overwrite, callback control, refcount takeover, or object confusion primitive is shown.

* High-control device API bonus: +0
  Although GPU command submission is user-shaped, the patch shows bounds validation for parser reads only, not attacker control over lifetime, refcounts, DMA ownership, or callback targets.

## 3. Reachability analysis

The likely trigger is a local user process able to access the amdgpu DRM interface and submit VCN decode messages through command submission. On many desktop or workstation deployments, render nodes may be available to unprivileged users in the video or render group, so PR:L is the practical assumption. Containers may inherit risk if GPU device nodes are passed through. The issue is not network reachable and requires affected AMDGPU VCN3 hardware and driver functionality.

## 4. Severity interpretation

This behaves like an actionable Moderate issue, not a clear Important-class vulnerability. The realistic impact is local denial of service through an OOB read during kernel parsing. Theoretical confidentiality impact is plausible because the primitive is an OOB read, but the patch does not show a user-visible leak or arbitrary read primitive. There is no evidence of OOB write or privilege escalation.

## 5. One-sentence report phrase

A local user with access to the amdgpu DRM interface can submit a malformed VCN3 decode message that causes out-of-bounds reads during BO-backed message parsing, potentially leading to kernel crash and limited confidentiality concern without evidence of direct privilege escalation.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED.
This should not be auto-closed because it is a local user-reachable GPU driver OOB read in a commonly exposed DRM command submission path, even though the currently supported impact is mainly DoS with only limited confidentiality concern.

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

Patch: drm/amdgpu/vcn3: Prevent OOB reads when parsing dec msg
Commit: 638d3e0b9eb77aa53fdd60e2b928761d16ba76fa
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=638d3e0b9eb77aa53fdd60e2b928761d16ba76fa

Commit description:

Check bounds against the end of the BO whenever we access the msg.

Signed-off-by: Benjamin Cheng <benjamin.cheng@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Ruijing Dong <ruijing.dong@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  drivers/gpu/drm/amd/amdgpu/vcn_v3_0.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=638d3e0b9eb77aa53fdd60e2b928761d16ba76fa

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

The original Linux kernel CVE announcement for CVE-2026-46230 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46230

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:L/PR:L/UI:N/S:U/C:L/I:N/A:H
  The Best / paranoid CVSS vector: AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H
  The Best / paranoid CVSS score: 7.1

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: 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).