[CVE-2026-64099][IMPORTANT] drm/v3d: Fix use-after-free of CPU job query arrays on error path [ Upstream

[CVE-2026-64099][IMPORTANT] drm/v3d: Fix use-after-free of CPU job query arrays on error path [ Upstream

[AL-KERNEL]

CVE: CVE-2026-64099
Priority: IMPORTANT
AL-KERNEL base severity: IMPORTANT
KPANIC flag: YES
Patch: drm/v3d: Fix use-after-free of CPU job query arrays on error path [ Upstream
Commit: acd55ea40d03e06f20a9986363019e0e5173990e
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=acd55ea40d03e06f20a9986363019e0e5173990e
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64099
Analysis date: Sun, 19 Jul 2026 22:57:38 -0400
ActionableScore: 7
ActionableScore lower bound: 6
Actionable bucket: Strong Important candidate / Actionable Moderate at minimum
Manual review required: YES

Summary:
A local use-after-free in the drm/v3d CPU job ioctl error path can read a freed cpu_job after cleanup, potentially causing a kernel crash and requiring manual review for possible UAF-based privilege escalation risk.

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ABOUT THIS REPORT
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The original Linux kernel CVE announcement for CVE-2026-64099 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64099

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: IMPORTANT
Manual review required: YES

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-2026-64099	IMPORTANT	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:H/I:H/A:H';*CWE-416;**CWE-476;*CWE-401;*CWE-772;Other CVSS 'AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:H';BEST CVSS score: '7';DESCR 'A use-after-free exists in the drm/v3d CPU job ioctl error path because the fail label can read cpu_job after v3d_job_cleanup has dropped the last reference and freed it. The same path can also become a NULL pointer dereference when early v3d_job_init failure zeroes the local pointer, and it leaks one syncobj reference per query because only the array storage was freed manually. For the CVSS the PR:L is used because a local process with access to the v3d DRM render device can reach the CPU job ioctl without full administrator privileges in common desktop or embedded deployments. The issue is not network reachable and requires local code execution on a system with the v3d driver and accessible DRM device nodes. Impact is at least local denial of service via kernel crash and in worst case may allow confidentiality or integrity impact due to the UAF and attacker influenced teardown state.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Strong Important candidate / Actionable Moderate at minimum (with actual score 7)  SKIP CVE-2026-64099 UNKNOWN SKIP No affected files built, so skip this CVE NO  - - unknown 	MAYBE	NULLPTR INIT LEAK ERRORPATH UAF HARDWARE LINUS  KPANIC INCREASED_TO_MODERATE_FROM_LOW_BASED_ON_GUESSCVSS KPANIC INCREASED_TO_HIGH_BASED_ON_ACTIONABLESCOREHIGHEREQTHAN7	-	-	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=7
ActionableScoreLower=6

## 1. ActionableScore

* Conservative score: 6
* Paranoid score: 7
* Final recommended bucket: **Strong Important candidate / Actionable Moderate at minimum**::

## 2. Signal breakdown

* Local unprivileged trigger: +1
  The vulnerable path is a DRM v3d CPU job ioctl, reachable by a local process with access to the v3d render device.

* Generic memory corruption: +2
  The commit explicitly describes a use-after-free where `cpu_job` is read after `v3d_job_cleanup()` drops the last reference and frees it.

* Real lifetime corruption: +1
  This is a kref lifetime bug involving cleanup after the object may already be freed.

* Reliable kernel crash / strong DoS: +1
  The same error path can also produce a NULL dereference, and UAF dereference in kernel ioctl cleanup is a realistic crash path.

* Weak LPE concern: +1
  The stale `cpu_job` fields are later used as `kvfree()` targets. No controlled reclaim or arbitrary write is demonstrated, so this is not strong LPE, but it is enough for manual-review sensitivity.

* Paranoid-only GPU ioctl lifetime/control concern: +1
  The ioctl handles user-created job/query state and syncobj references. The patch shows object lifetime and reference handling are directly involved, so the paranoid score treats this as a higher-risk local device-object API case.

No remote/network trigger is present. No admin-only penalty is applied because DRM render node access is commonly available to non-root local users in affected deployments.

## 3. Reachability analysis

A local user or local process with access to the v3d DRM render node can potentially reach the CPU job ioctl path. This is not network reachable. Containers or sandboxed workloads may matter if the DRM device node is passed through, because the attacker may not have host root but can still access the vulnerable ioctl. The issue is hardware and driver dependent, so it is not universal across all Linux systems, but on systems using v3d it is reachable through an ordinary local device interface.

Call-site confidence: high. The relevant error path, cleanup calls, destructor change, and scheduler free callback change are present in the provided patch.

## 4. Severity interpretation

This is stronger than an ordinary Moderate cleanup bug because the patch explicitly fixes a UAF, a NULL dereference, and a syncobj reference leak in an ioctl error path. Realistic demonstrated impact is local kernel crash or resource leak. Theoretical LPE concern exists because stale freed-object fields are read and used for cleanup, but the patch does not demonstrate attacker-controlled reclaim, object replacement, callback control, or arbitrary write. Therefore conservative handling is Actionable Moderate, while paranoid triage reaches Strong Important candidate.

## 5. One-sentence report phrase

A local use-after-free in the drm/v3d CPU job ioctl error path can read a freed cpu_job after cleanup, potentially causing a kernel crash and requiring manual review for possible UAF-based privilege escalation risk.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED. YES REQUIRES MANUAL CHECK.
Reason: explicit UAF in a local ioctl path, stale object fields used after free, and non-root render-node reachability make this unsuitable for auto-close.

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

Patch: drm/v3d: Fix use-after-free of CPU job query arrays on error path [ Upstream
Commit: acd55ea40d03e06f20a9986363019e0e5173990e
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=acd55ea40d03e06f20a9986363019e0e5173990e

Changed files:
  drivers/gpu/drm/v3d/v3d_sched.c
  drivers/gpu/drm/v3d/v3d_submit.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=acd55ea40d03e06f20a9986363019e0e5173990e

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

The original Linux kernel CVE announcement for CVE-2026-64099 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64099

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:L/I:L/A:H
  The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
  The Best / paranoid CVSS score: 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: 6
  Paranoid ActionableScore: 7

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: IMPORTANT
KPANIC detected for this report: YES
Published priority for this report (same as in Subject): IMPORTANT

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).