[CVE-2026-64051][IMPORTANT] accel/qaic: Add overflow check to remap_pfn_range during mmap [ Upstream

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

CVE: CVE-2026-64051
Priority: IMPORTANT
AL-KERNEL base severity: IMPORTANT
KPANIC flag: YES
Patch: accel/qaic: Add overflow check to remap_pfn_range during mmap [ Upstream
Commit: 9baafc2fea096279e75480f93fd5942e8336b510
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=9baafc2fea096279e75480f93fd5942e8336b510
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64051
Analysis date: Sun, 19 Jul 2026 17:33:46 -0400
ActionableScore: 8
ActionableScore lower bound: 7
Actionable bucket: Strong Important candidate / Actionable Moderate at minimum
Manual review required: YES

Summary:
The qaic mmap path could remap buffer object pages beyond the supplied VMA, leaving stale mappings after munmap() and creating a local use-after-free condition with possible denial of service or privilege escalation impact.

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ABOUT THIS REPORT
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The original Linux kernel CVE announcement for CVE-2026-64051 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64051

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-2026-64051	IMPORTANT	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:H/I:H/A:H';*CWE-416;*CWE-787;CWE-190;Other CVSS 'AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:H';BEST CVSS score: '7.8';DESCR 'qaic_gem_object_mmap() can call remap_pfn_range() with a length that extends past the supplied VMA when a buffer object scatter gather entry is larger than the remaining VMA range. This can create mappings outside the VMA, so a later munmap() removes only the original VMA range while extra PTE mappings may remain and refer to pages that can be freed or reused. For the CVSS the PR:L because a local user or process needs access to the qaic device mmap path, but full administrator privileges are not necessarily required where the accelerator device node is delegated. The issue is not network reachable. Impact is at least local denial of service and for the paranoid score is treated as possible local privilege escalation because stale writable mappings to freed pages can provide a memory corruption primitive.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Strong Important candidate / Actionable Moderate at minimum (with actual score 8)  SKIP CVE-2026-64051 UNKNOWN SKIP The Fixes patch not applied yet, so unlikely that actual: ff13be8303336ead5621712f2c55012d738878b5 YES  NO NO unknown 	MAYBE	READ UAF IMPROVEONLY  KPANIC INCREASED_TO_HIGH_BASED_ON_GUESSCVSS	-	-	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=8
ActionableScoreLower=7

## 1. ActionableScore

* Conservative score: 7
* Paranoid score: 8
* Final recommended bucket: **Strong Important candidate / Actionable Moderate at minimum**::

## 2. Signal breakdown

* Local unprivileged trigger: +1
  A local process with access to the qaic DRM or accel device mmap path can plausibly trigger the bug. Full host root is not inherently required if the device node is delegated to a user, service, render group, or container.

* Privilege escalation plausible: +2 paranoid, +1 conservative
  The patch explicitly says the overmapping can cause use-after-free issues after munmap() removes only the VMA region. Stale mappings to freed or reused pages are a plausible LPE-relevant primitive, although no complete reclaim or exploit chain is shown.

* Memory corruption, strong corruption primitive: +2
  remap_pfn_range() could map pages beyond the VMA boundary. This is not just validation cleanup, because it can leave PTE mappings outside the lifetime tracked by the VMA.

* Real lifetime corruption: +1
  The core issue is a mapping lifetime mismatch: munmap() unmaps the VMA but not the extra mappings created past the VMA range.

* Reliable kernel crash / strong DoS: +1
  A stale mapping to freed or reused memory can realistically lead to kernel instability or crash.

* Confidentiality impact plausible: +1
  Stale mappings may expose reused physical pages or kernel-managed memory contents depending on reuse behavior.

* Integrity impact plausible: +1
  If the mapping is writable, stale access to reused pages may corrupt data owned by another object or subsystem.

* Rare AND difficult-to-reach subsystem/configuration: -1
  qaic is hardware and driver specific. Exposure depends on Qualcomm AI accelerator availability and device node access.

## 3. Reachability analysis

The bug is locally reachable through qaic_gem_object_mmap() by a process that can open and mmap the qaic device object. It is not network reachable. Namespace and container impact depends on device delegation: a container or reduced-privilege service with access to the qaic device node could plausibly trigger it without full host-root privileges. The path is not a broad default Linux interface, because it requires the qaic driver and compatible hardware, but when present the mmap path is a normal user-facing device interface.

## 4. Severity interpretation

This is stronger than an ordinary Moderate because the patch context explicitly describes UAF caused by mappings beyond the VMA lifetime. The realistic evidence supports local memory lifetime corruption and DoS. The theoretical worst case supports possible privilege escalation because stale writable mappings to freed or reused pages can become a powerful memory corruption primitive. However, the patch does not demonstrate a complete exploit chain, attacker-controlled reclaim, or arbitrary write, so the conservative interpretation remains below high-end Critical handling.

## 5. One-sentence report phrase

The qaic mmap path could remap buffer object pages beyond the supplied VMA, leaving stale mappings after munmap() and creating a local use-after-free condition with possible denial of service or privilege escalation impact.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED

This should not be auto-closed because the patch explicitly mentions use-after-free and the affected code creates user-visible memory mappings whose lifetime can outlive the VMA. The combination of stale PTE mappings, freed or reused pages, and local device access is enough to require manual kernel security review.

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

Patch: accel/qaic: Add overflow check to remap_pfn_range during mmap [ Upstream
Commit: 9baafc2fea096279e75480f93fd5942e8336b510
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=9baafc2fea096279e75480f93fd5942e8336b510

Changed files:
  drivers/accel/qaic/qaic_data.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=9baafc2fea096279e75480f93fd5942e8336b510

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

The original Linux kernel CVE announcement for CVE-2026-64051 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64051

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: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: 7
  Paranoid ActionableScore: 8

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).