[CVE-2026-74445][MODERATE REGULAR] drm/vmwgfx: reject DX_BIND_QUERY without a DX context

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

CVE: CVE-2026-74445
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: drm/vmwgfx: reject DX_BIND_QUERY without a DX context
Commit: 7eae011829f94a76470ec76f016805f508437755
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=7eae011829f94a76470ec76f016805f508437755
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74445
Analysis date: Sat, 15 Aug 2026 12:19:27 -0400
ActionableScore: 4
ActionableScore lower bound: 3
Actionable bucket: Borderline Moderate / Actionable Moderate candidate
Manual review required: NO

Summary:
A local userspace process with access to a vmwgfx render node can submit a malformed DX_BIND_QUERY execbuf without a DX context, triggering a NULL pointer dereference and kernel oops, with impact limited to denial of service based on the patch evidence.

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

The original Linux kernel CVE announcement for CVE-2026-74445 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74445

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: NO

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-2026-74445	MODERATE	CHECK WITH IMPACT FROM ORIG NN MODERATE	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-476;*CWE-20;CWE-754;BEST CVSS score: '5.5';DESCR 'A NULL pointer dereference in the vmwgfx execbuf path can occur because vmw_cmd_dx_bind_query dereferences the DX context node even when no DX context was provided. A local userspace process with access to a vmwgfx render node can trigger this by submitting an execbuf with dx_context_handle set to SVGA3D_INVALID_ID and a SVGA_3D_CMD_DX_BIND_QUERY command. For the CVSS the PR:L because the attacker needs local code execution and access to the render node fd, but does not need full administrative privileges in typical render node deployments. The issue is not network reachable and is triggered through a local DRM ioctl command stream. Impact is denial of service via kernel oops or crash. The patch context supports a NULL dereference rather than UAF or arbitrary memory corruption, so confidentiality and integrity are not raised for the paranoid score.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline Moderate / Actionable Moderate candidate (with actual score 4)	YES	NULLPTR SIMPLEFIX HARDWARE LINUS  DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS_AND_CIANNH	NO	NO	checked

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

ActionableScore=4
ActionableScoreLower=3

## 1. ActionableScore

* Conservative score: 3
* Paranoid score: 4
* Final recommended bucket: **Borderline Moderate / Actionable Moderate candidate**

## 2. Signal breakdown

* Local unprivileged trigger: +1
  Any local userspace process with access to a vmwgfx render-node fd can submit the malformed execbuf.

* Reliable kernel crash / strong DoS: +1
  The commit explicitly describes a NULL pointer dereference and kernel oops via `sw_context->dx_ctx_node->ctx`.

* Broad/default/common subsystem or broadly deployed exposure: +1
  This is not a universal Linux path, but vmwgfx render nodes are commonly exposed in VMware guest deployments where this driver is used.

* Paranoid only: Availability impact realistic: +1
  The trigger appears simple and repeatable from a local render-node fd. If the environment treats oops as fatal or if repeated oopses destabilize the host guest kernel, availability impact is stronger.

Not applied:

* No generic memory corruption bonus. The patch supports NULL dereference, not UAF, OOB write, double-free, object reuse, or arbitrary write.
* No privilege escalation bonus. No reclaim, callback control, type confusion, writable stale object, or controlled corruption primitive is shown.
* No remote/network bonus. Trigger is local DRM ioctl/execbuf, not packet or network input.

## 3. Reachability analysis

The bug is reachable by local userspace through the vmwgfx DRM execbuf path when a render-node fd is available. In typical graphical or virtualized VMware guest environments, render nodes may be accessible to non-root users, so PR-like practical reachability is local unprivileged rather than admin-only.

Namespaces and containers may matter if `/dev/dri/renderD*` is passed into a container. Without device access, the bug is not reachable. The path is not network reachable and requires the vmwgfx driver and relevant virtual GPU stack.

Call-site confidence: high, because the patch and commit describe the exact dereference and the malformed command stream condition.

## 4. Severity interpretation

This behaves like a local denial-of-service issue, not an Important-class memory corruption vulnerability. The theoretical risk is limited because the primitive is a NULL pointer dereference rather than attacker-controlled memory corruption. Realistic exploitation evidence supports kernel oops/crash only.

The issue should not be treated as a strong LPE candidate based on the supplied patch. It is still worth manual review in affected VMware guest environments because render-node exposure can make the crash reachable by ordinary local users.

## 5. One-sentence report phrase

A local userspace process with access to a vmwgfx render node can submit a malformed DX_BIND_QUERY execbuf without a DX context, triggering a NULL pointer dereference and kernel oops, with impact limited to denial of service based on the patch evidence.

## 6. Manual review recommendation

MANUAL CHECK RECOMMENDED

Reason: local unprivileged render-node reachability plus reliable kernel oops makes this worth review for exposed vmwgfx deployments, but the patch does not support UAF, arbitrary corruption, or privilege escalation.

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

Patch: drm/vmwgfx: reject DX_BIND_QUERY without a DX context
Commit: 7eae011829f94a76470ec76f016805f508437755
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=7eae011829f94a76470ec76f016805f508437755

Commit description:

vmw_cmd_dx_bind_query() unconditionally dereferences
sw_context->dx_ctx_node->ctx.  Userspace can trigger a NULL pointer
dereference from any render-node fd by submitting an execbuf with
dx_context_handle == SVGA3D_INVALID_ID and a SVGA_3D_CMD_DX_BIND_QUERY
opcode in the command stream: dx_ctx_node is left NULL and the kernel
oopses on the assignment.  The same NULL is then re-read in
vmw_resources_reserve() via vmw_context_get_dx_query_mob().

All sibling DX handlers fail-close on a missing dx_ctx_node using
VMW_GET_CTX_NODE().  Use the same pattern here, returning -EINVAL up
front before any relocation state is published.

Fixes: 9c079b8 ("drm/vmwgfx: Adapt execbuf to the new validation api")
Cc: stable@vger.kernel.org
Assisted-by: Claude:claude-opus-4.7
Signed-off-by: Zack Rusin <zack.rusin@broadcom.com>
Reviewed-by: Ian Forbes <ian.forbes@broadcom.com>
Link: https://patch.msgid.link/20260505222728.519626-3-zack.rusin@broadcom.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  drivers/gpu/drm/vmwgfx/vmwgfx_execbuf.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=7eae011829f94a76470ec76f016805f508437755

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

The original Linux kernel CVE announcement for CVE-2026-74445 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74445

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: Not available
  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: 3
  Paranoid ActionableScore: 4

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).