[CVE-2026-63846][LOW] drm/amdgpu/jpeg: set no_user_fence for JPEG v3.0 ring [ Upstream

[CVE-2026-63846][LOW] drm/amdgpu/jpeg: set no_user_fence for JPEG v3.0 ring [ Upstream

[AL-KERNEL]

CVE: CVE-2026-63846
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: drm/amdgpu/jpeg: set no_user_fence for JPEG v3.0 ring [ Upstream
Commit: ee035a9d3eed3a9f5a3e83c31a10b321c9598861
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=ee035a9d3eed3a9f5a3e83c31a10b321c9598861
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-63846
Analysis date: Sun, 19 Jul 2026 11:10:56 -0400
ActionableScore: 2
ActionableScore lower bound: unknown
Actionable bucket: Ordinary Moderate / Low-like
Manual review required: NO

Summary:
A local user with access to the AMDGPU DRM render node may submit unsupported user-fence command streams to the JPEG v3.0 ring, causing a GPU hang or reset and resulting in local denial of service.

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

The original Linux kernel CVE announcement for CVE-2026-63846 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-63846

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.

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

CVE-2026-63846	LOW	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:N/I:N/A:H';*CWE-20;CWE-754;CWE-755;Other CVSS 'AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '5.5';DESCR 'The amdgpu JPEG v3.0 ring could accept command submissions with user fences even though this ring does not support 64 bit user fence writes. A local process with access to the DRM render node can submit such work and may trigger a GPU ring fault, GPU hang, or reset, causing a local denial of service. For the CVSS the PR:L is used because access to DRM render nodes is commonly granted to non root local users through render or video device permissions, but local code execution is still required. The issue is not network reachable and there is no clear kernel memory corruption primitive from the patch context. Impact is primarily availability loss, with no confirmed confidentiality or integrity impact.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like (with actual score 2)  SKIP CVE-2026-63846 UNKNOWN SKIP No affected files built, so skip this CVE NO  - - unknown 	MAYBE	SIMPLEFIX HARDWARE  INCREASED_FROM_LOW_BASED_ON_HIGHCVSSSCORE DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5 DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3	-	-	checked

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

ActionableScore=2

## 1. ActionableScore

* Conservative score: 2
* Paranoid score: 3
* Final recommended bucket: **Ordinary Moderate / Low-like**

## 2. Signal breakdown

Conservative signals:

* Local unprivileged trigger: +1
  A local process with access to the DRM render node can likely submit amdgpu CS work. This is commonly available to non-root users in the render or video group.
* Availability impact realistic: +1
  Submitting a user fence to a JPEG ring that does not support 64-bit user fence writes can plausibly cause a GPU ring fault, hang, reset, or local graphics/media DoS.

Paranoid additional signal:

* Reliable kernel crash / strong DoS: +1
  In the worst still-defensible interpretation, repeated invalid CS submissions could cause a persistent GPU reset loop or broader system availability degradation. This remains a DoS-only interpretation.

Negative / non-applied signals:

* No remote/network trigger: +0
  This is a local DRM command submission path, not a network reachable path.
* No generic memory corruption: +0
  The patch only sets `.no_user_fence = true`. It does not show UAF, OOB write, double free, type confusion, arbitrary write, or refcount misuse.
* No privilege escalation plausible: +0
  There is no concrete LPE primitive. User fences are rejected because the JPEG ring does not support them, not because the patch fixes an attacker-controlled kernel write.
* Hardware/path specificity limits exposure: implicit conservative handling
  The issue is specific to AMDGPU JPEG v3.0 rings, so it is not a broad core-kernel path.

## 3. Reachability analysis

The bug is triggerable by a local user or process that can access the AMDGPU DRM render node and submit command streams to the JPEG v3.0 ring. In many desktop or GPU-enabled server deployments, render node access is available to non-root users via device permissions, so PR:L is appropriate in CVSS-style reasoning.

Namespaces and containers can matter if `/dev/dri/renderD*` is passed into a container. A containerized workload with GPU device access may be able to reach the affected ioctl path, but this still requires local device access and is not remotely reachable by itself.

The path is hardware and driver specific. It requires affected AMDGPU hardware with JPEG v3.0 support and a configuration exposing the DRM render node. Realistic exploitation is limited to local DoS against GPU/media/graphics functionality, not demonstrated kernel memory corruption.

## 4. Severity interpretation

This behaves like an ordinary Moderate or Low-like local DoS issue. The patch is a validation/control flag change that prevents unsupported user fence submissions on a ring that cannot handle them.

Theoretical concern is limited to device or ring state corruption leading to GPU hang/reset. Realistic evidence supports availability impact only. There is no demonstrated confidentiality impact, integrity impact, privilege escalation path, UAF, OOB write, arbitrary write, or shared-page corruption primitive.

## 5. One-sentence report phrase

A local user with access to the AMDGPU DRM render node may submit unsupported user-fence command streams to the JPEG v3.0 ring, causing a GPU hang or reset and resulting in local denial of service.

## 6. Manual review recommendation

NO MANUAL CHECK NEEDED

This can be handled as a DoS-only validation fix unless additional evidence appears showing memory corruption, attacker-controlled write behavior, or cross-process GPU memory corruption.

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

Patch: drm/amdgpu/jpeg: set no_user_fence for JPEG v3.0 ring [ Upstream
Commit: ee035a9d3eed3a9f5a3e83c31a10b321c9598861
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=ee035a9d3eed3a9f5a3e83c31a10b321c9598861

Changed files:
  drivers/gpu/drm/amd/amdgpu/jpeg_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=ee035a9d3eed3a9f5a3e83c31a10b321c9598861

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

The original Linux kernel CVE announcement for CVE-2026-63846 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-63846

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:N/I:N/A:L
  The Best / paranoid CVSS vector: AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS score: 5.5

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: 2

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).