[CVE-2026-46204][MODERATE 7.0] drm/amdgpu/vcn4: Prevent OOB reads when parsing IB

[CVE-2026-46204][MODERATE 7.0] drm/amdgpu/vcn4: Prevent OOB reads when parsing IB

[AL-KERNEL]

CVE: CVE-2026-46204
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: drm/amdgpu/vcn4: Prevent OOB reads when parsing IB
Commit: 1dc005775fb5b3f86464406452b17364f85581d3
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=1dc005775fb5b3f86464406452b17364f85581d3
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46204
Analysis date: Sat, 01 Aug 2026 09:54:40 -0400
ActionableScore: 5
ActionableScore lower bound: 4
Actionable bucket: Actionable Moderate at minimum
Manual review required: YES

Summary:
A local user with access to AMDGPU render nodes may trigger OOB reads in the VCN4 IB parser by submitting malformed command buffers, potentially causing kernel or GPU driver DoS and limited information exposure, with manual review recommended due to parser-controlled downstream decisions.

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

The original Linux kernel CVE announcement for CVE-2026-46204 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46204

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.

======================================================================
AL-KERNEL CLASSIFICATION RESULT
======================================================================

CVE-2026-46204	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:L/I:L/A:H';CWE-125;*CWE-20;CWE-129;Other CVSS 'AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:H';BEST CVSS score: '6.6';DESCR 'Full SHA and stable kernel org link were not provided in the pasted GitHub view. The assessment assumes the commit titled drm/amdgpu/vcn4: Prevent OOB reads when parsing IB with short hash 2444eb0. Manual review is recommended because GPU command submission bugs with OOB reads can be more security relevant than a simple crash, especially on systems where render nodes are exposed to untrusted local users.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 5)  SKIP CVE-2026-46204  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
ActionableScoreLower=4

## 1. ActionableScore

* Conservative score: 4
* Paranoid score: 5
* Final recommended bucket: **Actionable Moderate at minimum**::

## 2. Signal breakdown

Conservative signals:

* Local unprivileged trigger: +1
  AMDGPU command submission through render nodes is commonly available to local non-root users in the render or video group.

* Reliable kernel crash / strong DoS: +1
  The parser performed direct reads from `ib->ptr` beyond validated IB bounds. Even if no write primitive is shown, invalid kernel-side reads during command parsing can plausibly crash or destabilize the GPU driver path.

* Confidentiality impact plausible: +1
  This is an OOB read from kernel-side IB memory. No clear user-visible disclosure path is shown, so this is limited and not treated as strong information disclosure.

* Broad/default/common subsystem exposure: +1
  AMDGPU render nodes are common on systems with AMD GPUs and are often intentionally exposed to local users.

Paranoid additional signal:

* Integrity impact plausible: +1
  OOB-read values can influence parser decisions, including engine type handling and message-buffer address selection. This is not a proven write primitive or LPE path, but it is enough to keep the issue out of auto-close territory.

Not counted:

* Remote/network reachable: +0
  This is a local GPU command submission issue.

* Strong LPE plausibility: +0
  The patch shows OOB reads, not UAF, OOB write, reclaim control, callback control, arbitrary write, or type confusion.

* High-control API bonus: +0
  GPU command submission is rich, but the patch does not show attacker control over object lifetime, allocator layout, callback targets, refcounts, DMA ownership, or page ownership.

## 3. Reachability analysis

A local user with access to the AMDGPU render device can likely submit malformed VCN IB command buffers and reach this parser. This normally does not require full root privileges if render nodes are exposed to users, which is common on desktop, workstation, and GPU compute systems. Containers may also expose render nodes deliberately, lowering practical privilege requirements inside those environments.

The path is not network reachable. The issue depends on AMDGPU VCN4 hardware and the relevant VCN decode or encode command path being available. Exploitation conditions are realistic for local users on affected AMD GPU systems, but the demonstrated primitive is an OOB read, not a controlled overwrite.

Call-site confidence: high for the immediate parser behavior, because the patch shows the direct unsafe reads and their replacement with `amdgpu_ib_get_value()`. Confidence is medium for downstream security impact because the full behavior of `vcn_v4_0_dec_msg()` and surrounding GPU job handling is not included.

## 4. Severity interpretation

This behaves like an actionable Moderate issue rather than an ordinary low-risk cleanup. The key reason is local user reachability through GPU command submission plus kernel-side OOB reads in a driver parser.

Realistically, the strongest supported impact is local DoS or GPU driver instability, with limited confidentiality concern from OOB reads. Theoretical integrity impact exists because invalid values can affect parsing decisions, but there is no demonstrated arbitrary write, UAF reclaim, or practical privilege-escalation primitive in the provided patch.

## 5. One-sentence report phrase

A local user with access to AMDGPU render nodes may trigger OOB reads in the VCN4 IB parser by submitting malformed command buffers, potentially causing kernel or GPU driver DoS and limited information exposure, with manual review recommended due to parser-controlled downstream decisions.

## 6. Manual review recommendation

MANUAL CHECK RECOMMENDED

The issue should not be auto-closed because it is a local GPU driver OOB read reachable from user-submitted command buffers, but the current patch does not support classifying it as strong memory corruption or a likely privilege-escalation vulnerability.

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

Patch: drm/amdgpu/vcn4: Prevent OOB reads when parsing IB
Commit: 1dc005775fb5b3f86464406452b17364f85581d3
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=1dc005775fb5b3f86464406452b17364f85581d3

Commit description:

Rewrite the IB parsing to use amdgpu_ib_get_value() which handles the
bounds checks.

Signed-off-by: Benjamin Cheng <benjamin.cheng@amd.com>
Acked-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_v4_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=1dc005775fb5b3f86464406452b17364f85581d3

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

The original Linux kernel CVE announcement for CVE-2026-46204 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46204

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:L/I:L/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: 4
  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).