[CVE-2026-68446][MODERATE REGULAR] drm/vmwgfx: Validate vmw_surface_metadata::array_size

[CVE-2026-68446][MODERATE REGULAR] drm/vmwgfx: Validate vmw_surface_metadata::array_size

[AL-KERNEL]

CVE: CVE-2026-68446
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: drm/vmwgfx: Validate vmw_surface_metadata::array_size
Commit: 5ff94e1279176b539d451e3e754fdcbd1a8d520a
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=5ff94e1279176b539d451e3e754fdcbd1a8d520a
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68446
Analysis date: Tue, 11 Aug 2026 21:10:47 -0400
ActionableScore: 4
ActionableScore lower bound: 3
Actionable bucket: Borderline Actionable Moderate / manual review recommended
Manual review required: YES

Summary:
A local user with access to the vmwgfx DRM device could provide an invalid Shader Model surface array size, causing inconsistent graphics resource metadata and possible local denial of service or driver instability.

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

The original Linux kernel CVE announcement for CVE-2026-68446 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68446

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.

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

CVE-2026-68446	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:L/UI:N/S:U/C:L/I:L/A:H';*CWE-20;CWE-1284;CWE-770;Other CVSS 'AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '5.8';DESCR 'A userspace controlled array_size field in drm/vmwgfx surface creation was not checked against the Shader Model specific maximum limits. A local user with access to the vmwgfx DRM device could submit an invalid surface array size and make the driver pass inconsistent surface metadata into the VMware graphics resource creation path. For the CVSS the PR:L is used because reliable triggering only requires a local process that can access the DRM ioctl, which is commonly available to non-root users through render or graphics device permissions. The issue is not network reachable. Impact is at least local denial of service or graphics driver instability. In the worst still defensible case, the invalid resource metadata may have limited confidentiality or integrity impact in later surface handling, so manual review is recommended.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline Actionable Moderate / manual review recommended (with actual score 4)	YES	SIMPLEFIX HARDWARE LINUS  INCREASED_FROM_LOW_BASED_ON_REQUIREMANUALCHECK DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5	YES	NO	checked

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

ActionableScore=4
ActionableScoreLower=3

## 1. ActionableScore

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

## 2. Signal breakdown

* Local unprivileged trigger: +1
  `array_size` is supplied through a DRM ioctl. On typical desktop or VMware guest setups, DRM render or graphics device access may be available to a non-root local user.

* Weak/indirect corruption candidate: +1
  The patch validates a userspace-controlled resource metadata field before it is used in the vmwgfx surface creation path. The diff does not show a concrete OOB write, UAF, arbitrary write, refcount issue, or callback corruption, so this is not a strong memory corruption primitive.

* Availability impact plausible: +1
  Invalid surface metadata can plausibly cause vmwgfx driver instability, device-side failure, or local DoS, but the commit does not provide a crash trace or demonstrated panic.

* Paranoid validation/device-metadata concern: +1
  The issue was reported by ZDI and affects GPU surface metadata passed into a trusted virtual graphics resource path. This supports manual review, but not an Important-level score without a concrete downstream primitive.

* Validation-only cap applies
  This is primarily an input-validation fix returning `-EINVAL` for unsupported `array_size` values. No demonstrated UAF, OOB write, arbitrary write, or info leak is shown, so conservative scoring should stay capped below Important.

## 3. Reachability analysis

A local process with access to the vmwgfx DRM device can trigger the affected ioctl path by requesting a GB surface with an oversized `array_size`. This does not appear network reachable. Namespaces or containers matter only if the DRM device is passed through or exposed to the container. The path is relevant mainly to VMware virtual GPU environments, so exposure is narrower than core DRM or generic kernel paths, but it is still reachable through an ordinary local device interface when vmwgfx is present.

Call-site confidence: medium. The patch shows the validation site in `vmw_gb_surface_define_internal()`, but not the full downstream surface allocation and host-command handling path.

## 4. Severity interpretation

This behaves more like a borderline actionable Moderate than an Important-class issue. Theoretical concern exists because untrusted userspace controls graphics resource metadata that is consumed by a privileged kernel driver and virtual GPU backend. Realistic exploitation evidence is limited because the patch only shows missing bounds validation and does not demonstrate memory corruption, disclosure, privilege escalation, or a reliable host-wide crash.

## 5. One-sentence report phrase

A local user with access to the vmwgfx DRM device could provide an invalid Shader Model surface array size, causing inconsistent graphics resource metadata and possible local denial of service or driver instability.

## 6. Manual review recommendation

MANUAL CHECK RECOMMENDED

Manual review is recommended because the field is userspace-controlled, the affected path is a GPU resource creation ioctl, and the issue was reported by ZDI. However, the patch does not show a concrete exploit primitive, so it should not be treated as a Strong Important candidate without additional evidence.

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

Patch: drm/vmwgfx: Validate vmw_surface_metadata::array_size
Commit: 5ff94e1279176b539d451e3e754fdcbd1a8d520a
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=5ff94e1279176b539d451e3e754fdcbd1a8d520a

Commit description:

This field comes from userspace and should be validated against specific
limits depending on which Shader Model (SM) is available.

Fixes: 504901d ("drm/vmwgfx: Refactor surface_define to use vmw_surface_metadata")
Reported-by: Zero Day Initiative <zdi-disclosures@trendmicro.com>
Cc: stable@vger.kernel.org
Signed-off-by: Ian Forbes <ian.forbes@broadcom.com>
Reviewed-by: Maaz Mombasawala <maaz.mombasawala@broadcom.com>
Signed-off-by: Zack Rusin <zack.rusin@broadcom.com>
Link: https://patch.msgid.link/20260623193314.506257-1-ian.forbes@broadcom.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  drivers/gpu/drm/vmwgfx/vmwgfx_surface.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=5ff94e1279176b539d451e3e754fdcbd1a8d520a

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

The original Linux kernel CVE announcement for CVE-2026-68446 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68446

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:H
  The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:H
  The Best / paranoid CVSS score: 5.8

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).