[CVE-2026-64008][IMPORTANT] accel/rocket: fix UAF via dangling GEM handle in create_bo [ Upstream

[CVE-2026-64008][IMPORTANT] accel/rocket: fix UAF via dangling GEM handle in create_bo [ Upstream

[AL-KERNEL]

CVE: CVE-2026-64008
Priority: IMPORTANT
AL-KERNEL base severity: IMPORTANT
KPANIC flag: YES
Patch: accel/rocket: fix UAF via dangling GEM handle in create_bo [ Upstream
Commit: 18abd88d19ea195e2e1547fca0970c2f91d77a42
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=18abd88d19ea195e2e1547fca0970c2f91d77a42
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64008
Analysis date: Sun, 19 Jul 2026 19:27:11 -0400
ActionableScore: 7
ActionableScore lower bound: 6
Actionable bucket: Strong Important candidate / Actionable Moderate at minimum
Manual review required: YES

Summary:
A local UAF in the accel/rocket GEM BO creation path leaves a live file IDR handle pointing to freed slab memory, allowing later ioctls to dereference the freed object and potentially cause a kernel crash or local privilege escalation.

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

The original Linux kernel CVE announcement for CVE-2026-64008 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64008

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-2026-64008	IMPORTANT	CHECK WITH IMPACT FROM ORIG NN LOW	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H';*CWE-416;*CWE-672;CWE-754;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H';BEST CVSS score: '7.8';DESCR 'A use-after-free in the accel/rocket DRM BO creation path occurs because rocket_ioctl_create_bo creates a live GEM handle before several fallible operations complete. If sg table allocation, drm_mm insertion, or IOMMU mapping fails, the error path can free the GEM object while the per file IDR still contains a handle to the freed object. A local user can then trigger later ioctls such as PREP_BO, FINI_BO, or SUBMIT with that dangling handle and make drm_gem_object_lookup return freed memory. For the CVSS the PR:L is used because exploitation requires local access to the DRM accel device or a process context allowed to issue these ioctls, not full administrator privileges. The issue is not network reachable. Impact is at least local denial of service and may allow privilege escalation because the bug provides a kernel UAF primitive in a device ioctl path.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Strong Important candidate / Actionable Moderate at minimum (with actual score 7)  SKIP CVE-2026-64008 UNKNOWN SKIP No affected files built, so skip this CVE NO  - - unknown 	MAYBE	ERRORPATH UAF LINUS KPANIC MEMORY  KPANIC INCREASED_TO_HIGH_BASED_ON_GUESSCVSS	-	-	checked

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

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**
  A local process with access to the accel/DRM device node can call `CREATE_BO` and then later ioctls using the returned dangling handle.

* **Privilege escalation plausible: +1 conservative / +2 paranoid**
  Conservative: UAF is real, but the patch does not demonstrate controlled reclaim, overwrite, callback control, or type confusion.
  Paranoid: this is a kernel UAF in a DRM/accel ioctl object-lifetime path with attacker-controlled ioctl sequencing, so LPE is technically plausible and requires manual review.

* **Generic memory corruption, strong primitive: +2**
  The commit explicitly describes a dangling GEM handle in the file IDR pointing to freed slab memory, followed by `drm_gem_object_lookup()` returning freed memory.

* **Real lifetime corruption: +1**
  This is a stale handle / stale pointer after object free, caused by freeing the GEM object without removing the handle from the IDR.

* **Reliable kernel crash / strong DoS: +1**
  Subsequent `PREP_BO`, `FINI_BO`, or `SUBMIT` ioctls can dereference freed memory and plausibly crash the kernel.

* **Local high-control device object lifetime API: +1**
  The affected path is a DRM/accel ioctl interface where userspace controls GEM BO creation and later object-handle use. This applies because the patch shows direct influence over object lifetime and handle reuse.

* **Rare or hardware-specific exposure: -1**
  The issue requires the `accel/rocket` driver and accessible device node, so exposure is narrower than common core kernel paths.

## 3. Reachability analysis

The bug is locally reachable by a user or process that can open the affected accel/DRM device and issue the relevant ioctls. It is not network reachable. Namespaces do not inherently grant access, but containers or service sandboxes with delegated GPU or accel device access may be affected without full host-root privileges. Typical exploitation requires the Rocket accelerator driver, the device node, and an error after handle creation but before BO setup completes, such as sg table allocation, drm_mm insertion, or IOMMU mapping failure. Call-site confidence: **high**, because the commit identifies the later handle users and the patch shows the vulnerable create path.

## 4. Severity interpretation

This behaves like an **Actionable Moderate to Strong Important candidate**, not an ordinary Moderate. The realistic demonstrated impact is local kernel UAF and likely DoS. The theoretical higher impact is local privilege escalation through reuse of freed GEM object memory, but the patch does not prove a controlled reclaim or write primitive. Therefore the conservative score stays at 6, while the paranoid score is 7 due to the explicit UAF in a local device ioctl path.

## 5. One-sentence report phrase

A local UAF in the accel/rocket GEM BO creation path leaves a live file IDR handle pointing to freed slab memory, allowing later ioctls to dereference the freed object and potentially cause a kernel crash or local privilege escalation.

## 6. Manual review recommendation

**MANUAL CHECK REQUIRED**

This is a confirmed kernel UAF with a stale userspace-visible handle and later ioctl dereference path, so it should not be auto-closed even if practical LPE depends on allocator reuse and device availability.

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

Patch: accel/rocket: fix UAF via dangling GEM handle in create_bo [ Upstream
Commit: 18abd88d19ea195e2e1547fca0970c2f91d77a42
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=18abd88d19ea195e2e1547fca0970c2f91d77a42

Changed files:
  drivers/accel/rocket/rocket_gem.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=18abd88d19ea195e2e1547fca0970c2f91d77a42

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

The original Linux kernel CVE announcement for CVE-2026-64008 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64008

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:H/I:H/A:H
  The Best / paranoid CVSS vector: AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
  The Best / paranoid CVSS score: 7.8

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: 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).