[CVE-2026-80701][MODERATE REGULAR] drm/vmwgfx: enforce cursor size limits for MOB cursors

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

CVE: CVE-2026-80701
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: drm/vmwgfx: enforce cursor size limits for MOB cursors
Commit: 1eb4f796695be39e0b5c4383350033ced9ade703
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=1eb4f796695be39e0b5c4383350033ced9ade703
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80701
Analysis date: Fri, 28 Aug 2026 04:41:00 -0400
ActionableScore: 3
ActionableScore lower bound: unknown
Actionable bucket: Borderline. Manual review recommended
Manual review required: YES

Summary:
No one-sentence report phrase was found.

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

The original Linux kernel CVE announcement for CVE-2026-80701 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80701

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-2026-80701	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 'An oversized MOB cursor request in drm/vmwgfx can leave vps cursor mob as NULL because vmw_cursor_mob_get can fail after size checks are missed on the modern SVGA_CAP2_CURSOR_MOB path. The later cursor update path can still call vmw_bo_map_and_cache on this NULL backing object and crash the kernel through a NULL pointer dereference. For the CVSS the PR:L is used because the attacker normally needs local DRM master access, such as a local graphical session or another process that can control the DRM cursor plane, but full administrator privileges are not required in that model. The issue is not network reachable and is triggered through DRM_IOCTL_MODE_CURSOR2 with an oversized cursor width or height. Impact is denial of service via kernel crash. No UAF, OOB write, arbitrary write, or information disclosure primitive is supported by the patch context, so confidentiality and integrity remain unaffected.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline. Manual review recommended (with actual score 3)	YES	DANGER NOMEMCHK HARDWARE LINUS  DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS_AND_CIANNH	YES	NO	checked

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

ActionableScore=3

1. ActionableScore
* Conservative score: 3
* Paranoid score: 3
* Final recommended bucket: **Borderline. Manual review recommended**::

2. Signal breakdown
* Local unprivileged trigger: +1. The bug is reachable from a local process with DRM master access via DRM_IOCTL_MODE_CURSOR2, and this does not necessarily require full host root in a graphical session model.
* Reliable kernel crash / strong DoS: +1. The commit describes a NULL pointer dereference in vmw_bo_map_and_cache_size() after vmw_bo_map_and_cache(NULL).
* Availability impact realistic: +1. The oversized cursor request is simple and can plausibly produce a host kernel oops or crash in affected vmwgfx environments.
* No generic memory corruption: +0. The evidence supports NULL dereference, not UAF, OOB write, double free, type confusion, or arbitrary write.
* No confidentiality or integrity impact: +0. There is no supported disclosure or write primitive.
* No remote reachability: +0. The path is a local DRM ioctl path, not packet or network input.

3. Reachability analysis
A local attacker needs access to the vmwgfx DRM device and DRM master capability, such as a local graphical session or a process controlling the cursor plane. This is not normally reachable from the network. Containers or delegated graphics access may reduce the practical privilege boundary, so PR:L is more appropriate than PR:H for triage. The affected path is specific to VMware vmwgfx and the modern SVGA_CAP2_CURSOR_MOB cursor path, which is common on modern VMware hosts but not a broad default path on all Linux systems.

4. Severity interpretation
This behaves like an actionable local DoS rather than an Important class vulnerability. The realistic impact is kernel crash through a NULL pointer dereference. Theoretical privilege escalation is not supported by the patch because there is no UAF, reclaim, controlled overwrite, callback corruption, type confusion, or information leak. Manual review is still useful because the crash is reachable through a local DRM ioctl path with non-root DRM master access in some deployments.

5. One-sentence report phrase
An oversized MOB cursor request in drm/vmwgfx can leave the cursor backing object NULL and later crash the kernel when the MOB update path maps it, requiring local DRM master access and causing denial of service only.

6. Manual review recommendation
MANUAL CHECK RECOMMENDED. The issue is not an Important candidate based on current evidence, but local DRM master reachability and reliable kernel crash make it inappropriate for fully automatic low-priority closure without checking product exposure to vmwgfx.

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

Patch: drm/vmwgfx: enforce cursor size limits for MOB cursors
Commit: 1eb4f796695be39e0b5c4383350033ced9ade703
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=1eb4f796695be39e0b5c4383350033ced9ade703

Commit description:

vmw_cursor_plane_atomic_check() bounds cursor width and height only
on the legacy update path; the SVGA_CAP2_CURSOR_MOB path -- the
default on modern hosts -- accepts any size.  When the requested size
exceeds SVGA_REG_CURSOR_MAX_DIMENSION or SVGA_REG_MOB_MAX_SIZE,
vmw_cursor_mob_get() returns -EINVAL and leaves vps->cursor.mob NULL.
Its return value is then discarded in vmw_cursor_plane_prepare_fb(),
so the subsequent vmw_cursor_update_mob() calls
vmw_bo_map_and_cache(NULL) and oopses inside
vmw_bo_map_and_cache_size() on the tbo.base.size load.

Reachable from any DRM master via DRM_IOCTL_MODE_CURSOR2 with a
sufficiently large width or height (e.g. cursor_max_dim + 1).

Reject oversized cursors in atomic_check for both MOB-backed cursor
update types.  The MOB byte-size limit only applies to the
SVGA_CAP2_CURSOR_MOB path (vmw_cursor_mob_size() returns 0 for
GB_ONLY); compute the required MOB size in 64-bit to avoid overflow
when very large dimensions are requested.

In prepare_fb only call vmw_cursor_mob_get()/_map() for
VMW_CURSOR_UPDATE_MOB -- the GB_ONLY path uses bo->map.virtual
directly and would otherwise be silently downgraded to NONE on hosts
without SVGA_CAP2_CURSOR_MOB (where vmw_cursor_mob_get() always
returns -EINVAL).  Degrade the update to NONE if vmw_cursor_mob_get()
or vmw_cursor_mob_map() fails so the update path does not run with a
NULL backing MOB.

Fixes: 9655441 ("drm/vmwgfx: Refactor cursor handling")
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/20260505222728.519626-10-zack.rusin@broadcom.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  drivers/gpu/drm/vmwgfx/vmwgfx_cursor_plane.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=1eb4f796695be39e0b5c4383350033ced9ade703

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

The original Linux kernel CVE announcement for CVE-2026-80701 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80701

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: unknown
  Paranoid ActionableScore: 3

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).