[CVE-2026-98608][LOW] drm/virtio: fix object leak in virtio_gpu_resource_create_ioctl() [ Upstream

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

CVE: CVE-2026-98608
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: drm/virtio: fix object leak in virtio_gpu_resource_create_ioctl() [ Upstream
Commit: d33d5ef8225538f76e4598c09e2074834667bb8d
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=d33d5ef8225538f76e4598c09e2074834667bb8d
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98608
Analysis date: Mon, 19 Oct 2026 03:41:10 -0400
ActionableScore: 1
ActionableScore lower bound: unknown
Actionable bucket: Ordinary Moderate
Manual review required: NO

Summary:
An incorrect GEM reference cleanup on the virtio GPU resource creation error path leaks guest and host-side resources, but reliable accumulation to host-wide denial of service and below-host-admin triggerability are not established.

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

The original Linux kernel CVE announcement for CVE-2026-98608 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98608

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.

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

CVE-2026-98608	LOW	https://www.kernelcve.org/list/?q=CVE-2026-98608 CHECK WITH IMPACT FROM ORIG NN LOW | AEGIS IMPACT LOW AEGIS_AS=1 LEGACY=LOW RESULT=SAME (final reconciliation agrees; DECISION: both 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:N/I:N/A:H';*CWE-401;*CWE-772;CWE-404;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '4.7';DESCR 'An incorrect reference cleanup in virtio_gpu_resource_create_ioctl can retain a virtio GPU object when GEM handle creation fails. The leaked state includes the object pages, sg table, resource ID, and the corresponding host side resource. Repeated successful access to this error path could increase memory and GPU backend resource consumption and may eventually cause denial of service, but the patch does not establish immediate host wide exhaustion from a single or small number of operations. For the CVSS the PR:L value is used because a local process must have access to the virtio GPU DRM interface and issue the resource creation ioctl. AC:H is used because drm_gem_handle_create must fail after the GPU object and its resources have already been created, and reliable attacker control over that specific failure is not demonstrated. The issue is not network reachable. The demonstrated primitive is persistent resource retention with no supported UAF, OOB access, information disclosure, arbitrary write, or privilege escalation. Automated impact decision path. The original SimpleNet classifier selected LOW. The primary LLM estimated paranoid CVSS 4.7 and the production ActionableScore returned 1 with recommendation Ordinary Moderate. The production rules then evaluated CVSS thresholds and ActionableScore thresholds. No severity changing production threshold or specialist override was recorded. The legacy KP specialist has no review artifact for this run. The legacy FD or DH downgrade specialist has no review artifact for this run. The independent weaker Aegis shadow evaluated CVSS 4.9 and ActionableScore 1 with primitive class CLASS_C and manual review RECOMMENDED. Its independently reconciled impact was LOW. The shadow agreed with the final production impact and aggregation did not change that impact. The final reported impact is LOW.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 1)	MAYBE	VIRT SIMPLEFIX LEAK ERRORPATH HARDWARE LINUS 	-	-	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=1
PrimitiveClass=CLASS_C
RealUAF=NO
HostAdminRequired=UNKNOWN
NamespaceScopedPrivilege=UNKNOWN
ImportantCandidate=NO
ManualReview=NO
AutoDowngradeAllowed=YES
RequiresHostUID0=UNKNOWN
AuthorizationDecisionBypass=NO
ProtectedResourceImpact=NONE
B4PendingReview=NO
B4PendingConfirmed=NO

1. ActionableScore

* Raw conservative score: 1
* Conservative score: 1
* Raw paranoid score: 1
* Paranoid score: 1
* No floor or cap was applied.
* Final recommended bucket: **Ordinary Moderate**::

2. Signal breakdown

* +1 Concrete persistent kernel resource/reference leak. On failure of `drm_gem_handle_create()`, the owned GEM reference is not dropped, preventing `obj->funcs->free()` from releasing the `virtio_gpu_object`, pages, SG table, resource ID, and host-side resource.
* +0 Resource exhaustion. Accumulation is possible, but reliable repeated access to the leaking branch is not established because handle creation must fail after resource allocation succeeds.
* +0 Local unprivileged trigger. The ioctl is a plausible render-node operation, but the supplied context does not establish device permissions or complete below-host-admin reachability.
* No privilege penalty was applied because host-admin-equivalent privilege is not positively established.
* No OOB read or write, UAF, double release, refcount mutation through freed storage, arbitrary write, shared-backing modification, or authorization bypass is present.
* No crash point was awarded because host-wide failure is not demonstrated.
* NEW52 B5-R does not apply because there is no heap OOB write or retry-accumulated offset.
* NEW53 B3-PENDING does not apply because no shared or file-backed storage is modified.
* V33 and V32 do not apply because no attacker-influenced active structured state or checksum metadata is corrupted.
* B4-PENDING does not apply because no DENY-to-ALLOW authorization decision changes.

3. Reachability analysis

The leaking path is reached through `virtio_gpu_resource_create_ioctl()`. A process must access the relevant DRM device, successfully create the underlying GPU resource, and then encounter failure in `drm_gem_handle_create()`. The patch does not show the ioctl registration flags, device-node permissions, or whether an ordinary user, compositor, delegated graphics service, or administrator performs the complete sequence.

`HostAdminRequired` and `NamespaceScopedPrivilege` therefore remain `UNKNOWN`. No network trigger, namespace-specific capability path, special physical hardware requirement, or race is established. The main uncertainty is whether an attacker can reliably force and repeat the specific handle-creation failure while earlier allocations continue succeeding.

4. Primitive and severity interpretation

The exact primitive is a persistent ownership/reference leak caused by using `drm_gem_object_release()` where `drm_gem_object_put()` is required. This is not a stale post-lifetime access. The object remains alive because its owned reference is retained, so `RealUAF=NO`.

The demonstrated consequence is retention of guest-kernel and host-side graphics resources. Eventual resource exhaustion is plausible under repeated failures but is not demonstrated as reliable or host-wide. There is no evidence of memory corruption, protected-state modification, confidentiality loss, privilege escalation, or a guest-to-host corruption primitive.

The issue is therefore `CLASS_C`, not an Important-preserving Class A or Class B primitive. `ImportantCandidate=NO` and `AutoDowngradeAllowed=YES` because only resource retention is established and no unresolved corruption or security-boundary mechanism remains.

5. One-sentence report phrase

An incorrect GEM reference cleanup on the virtio GPU resource creation error path leaks guest and host-side resources, but reliable accumulation to host-wide denial of service and below-host-admin triggerability are not established.

6. Manual review recommendation

NO MANUAL CHECK NEEDED

The patch establishes a conventional resource leak without memory corruption, authorization bypass, cross-boundary write, or a reliable strong denial-of-service primitive.

7. Call-site confidence

Call-site confidence: medium

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

Patch: drm/virtio: fix object leak in virtio_gpu_resource_create_ioctl() [ Upstream
Commit: d33d5ef8225538f76e4598c09e2074834667bb8d
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=d33d5ef8225538f76e4598c09e2074834667bb8d

Changed files:
  drivers/gpu/drm/virtio/virtgpu_ioctl.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=d33d5ef8225538f76e4598c09e2074834667bb8d

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

The original Linux kernel CVE announcement for CVE-2026-98608 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98608

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:H/PR:L/UI:N/S:U/C:N/I:N/A:L
  The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS score: 4.7

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: 1

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).