[CVE-2026-74423][LOW] accel/amdxdna: Fix leak when pinning ubuf pages [ Upstream

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

CVE: CVE-2026-74423
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: accel/amdxdna: Fix leak when pinning ubuf pages [ Upstream
Commit: 68dc52f308a17c3103a349f722dd5dea32c50a88
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=68dc52f308a17c3103a349f722dd5dea32c50a88
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74423
Analysis date: Sat, 15 Aug 2026 17:01:03 -0400
ActionableScore: 2
ActionableScore lower bound: 1
Actionable bucket: Ordinary Moderate / Low-like
Manual review required: NO

Summary:
A local amdxdna user buffer import failure can leak partially pinned user pages when pin_user_pages_fast() returns fewer pages than requested, allowing repeated local attempts to cause resource exhaustion but not indicating memory corruption or privilege escalation.

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

The original Linux kernel CVE announcement for CVE-2026-74423 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74423

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
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CVE-2026-74423	LOW	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:N/I:N/A:H';*CWE-772;*CWE-401;**CWE-400;Other CVSS 'AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '5.5';DESCR 'A resource leak in amdxdna user buffer import can occur when pin_user_pages_fast returns a partial success and fewer pages are pinned than requested. The already pinned pages may not be released on the failure path, allowing repeated local attempts to keep user pages pinned and consume memory or pinned page accounting. For the CVSS the PR:L is used because a local process with access to the amdxdna device interface can provide the user buffer and request page pinning, while administrative privileges are not inherently indicated. The issue is not network reachable and requires local code execution. Impact is denial of service through resource exhaustion. For the paranoid score, A:H is used only for sustained repeated failures that can realistically exhaust memory or pin accounting. No confidentiality or integrity impact is assigned because the patch shows a resource leak rather than UAF, OOB access, or an arbitrary write primitive.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like (with actual score 2)  SKIP CVE-2026-74423 UNKNOWN SKIP No affected files built, so skip this CVE NO  - - unknown 	MAYBE	NOMEMCHK SIMPLEFIX LEAK MEMORY  DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS_AND_CIANNH DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3	-	-	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=2
ActionableScoreLower=1

## 1. ActionableScore

* Conservative score: 1
* Paranoid score: 2
* Final recommended bucket: **Ordinary Moderate / Low-like**::

## 2. Signal breakdown

Conservative signals:

* Local unprivileged trigger: +1. A local process with access to the amdxdna device interface can submit a user allocated buffer and reach the page pinning path.
* Availability impact realistic: +1. Repeated partial pin failures can leak pinned pages and consume memory or pinned page accounting.
* Rare AND difficult-to-reach subsystem/configuration: -1. The issue requires amdxdna hardware, the amdxdna driver, and access to the relevant accelerator device node.

Paranoid additional signal:

* Reliable kernel crash / strong DoS: +1. If an attacker can repeatedly force partial pin_user_pages_fast() success, the leaked long-term page pins may cause stronger system-wide resource exhaustion.

Signals not applied:

* No remote reachable signal. This is a local device API path.
* No firmware-mediated external influence. The bug is in local user buffer import error handling.
* No generic memory corruption. The patch shows leaked page pins, not UAF, double free, OOB write, type confusion, or arbitrary write.
* No privilege escalation signal. There is no supported reclaim, overwrite, callback, refcount takeover, or object confusion primitive.
* No confidentiality or integrity impact. The effect is resource leakage and availability degradation.

## 3. Reachability analysis

The likely trigger is a local process that can open and use the amdxdna accelerator device interface, commonly through a device node exposed to a user or accelerator/render group. Namespaces or containers do not automatically make this reachable unless the device node is passed through or delegated. The path is not network reachable and is only relevant on systems with AMD XDNA hardware and the amdxdna driver enabled. Practical exploitation also depends on being able to cause partial pin_user_pages_fast() success, which is plausible but not shown as a simple one-shot crash primitive in the patch.

Call-site confidence: medium. The changed function and cleanup behavior are visible, but broader ioctl and device-node permission context is not fully shown in the provided patch.

## 4. Severity interpretation

This behaves more like an ordinary Moderate or Low-like resource exhaustion issue than an Important-class vulnerability. The theoretical worst case is local denial of service by leaking long-term pinned pages through repeated failed imports. The realistic evidence does not show memory corruption, privilege escalation, sensitive data exposure, or a cross-boundary ownership violation.

## 5. One-sentence report phrase

A local amdxdna user buffer import failure can leak partially pinned user pages when pin_user_pages_fast() returns fewer pages than requested, allowing repeated local attempts to cause resource exhaustion but not indicating memory corruption or privilege escalation.

## 6. Manual review recommendation

NO MANUAL CHECK NEEDED

This is a resource leak without a demonstrated memory corruption or security-boundary bypass primitive, and the exposure is limited to local access to a niche accelerator device path.

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

Patch: accel/amdxdna: Fix leak when pinning ubuf pages [ Upstream
Commit: 68dc52f308a17c3103a349f722dd5dea32c50a88
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=68dc52f308a17c3103a349f722dd5dea32c50a88

Changed files:
  drivers/accel/amdxdna/amdxdna_ubuf.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=68dc52f308a17c3103a349f722dd5dea32c50a88

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

The original Linux kernel CVE announcement for CVE-2026-74423 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74423

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:N/I:N/A:L
  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: 1
  Paranoid ActionableScore: 2

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).