[CVE-2026-64054][MODERATE 7.0] net: shaper: reject duplicate leaves in GROUP request [ Upstream

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

CVE: CVE-2026-64054
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: net: shaper: reject duplicate leaves in GROUP request [ Upstream
Commit: 5098b223f0f0c5c18a3884a8b0ea5bd4a0c7bd75
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=5098b223f0f0c5c18a3884a8b0ea5bd4a0c7bd75
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64054
Analysis date: Sun, 19 Jul 2026 17:48:56 -0400
ActionableScore: 7
ActionableScore lower bound: 4
Actionable bucket: Strong Important candidate / Actionable Moderate at minimum
Manual review required: YES

Summary:
A duplicate `NET_SHAPER_A_LEAVES` entry in a GROUP request can cause the same parent object to be queued twice for cleanup, leading to a kernel double free reachable through local Generic Netlink network-shaper control operations.

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ABOUT THIS REPORT
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The original Linux kernel CVE announcement for CVE-2026-64054 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64054

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: MODERATE 7.0
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-2026-64054	MODERATE	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-415;*CWE-20;*CWE-664;Other CVSS 'AV:L/AC:L/PR:H/UI:N/S:U/C:L/I:L/A:H';BEST CVSS score: '7.8';DESCR 'NET_SHAPER_A_LEAVES parsing allowed the same leaf handle to appear more than once in a GROUP request. This can place the same old parent object into the cleanup list more than once and the error path can free the same parent twice, which is a kernel double free memory corruption condition. The trigger is local control plane access through Generic Netlink rather than packet traffic, so it is not directly network reachable. For the CVSS the PR:L is used for the paranoid score because delegated CAP_NET_ADMIN or container level network administration may be enough to send the request in some deployments, although full host administration may be required on stricter systems. Impact is at least denial of service via kernel crash and in worst case may allow confidentiality and integrity impact due to heap memory corruption, so manual review is required.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Strong Important candidate / Actionable Moderate at minimum (with actual score 6)	YES	DANGER HARDWARE KPANIC  KPANIC INCREASED_TO_HIGH_BASED_ON_GUESSCVSS KPANIC DECREASED_TO_MODERATE70_BASED_ON_ACTIONABLESCORELOWERTHAN7	YES	NO	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=7
ActionableScoreLower=4

## 1. ActionableScore

* Conservative score: **4**
* Paranoid score: **7**
* Final recommended bucket: **Strong Important candidate / Actionable Moderate at minimum**

## 2. Signal breakdown

Paranoid score signals:

* **Memory corruption, strong corruption primitive: +2**. The commit explicitly states that duplicate leaves can cause the same old parent pointer to be placed twice in `old_nodes[]`, leading to a double free.
* **Real lifetime corruption: +1**. This is a real object lifetime bug involving duplicate cleanup of the same parent object.
* **Reliable kernel crash / strong DoS: +1**. A double free in kernel cleanup paths is a realistic crash condition.
* **Privilege escalation plausible: +2**. Kernel double free can plausibly become heap memory corruption exploitable beyond DoS, although the patch does not demonstrate a concrete reclaim or overwrite primitive.
* **Confidentiality impact plausible: +1**. In the paranoid interpretation, successful heap corruption exploitation may affect confidentiality.
* **Integrity impact plausible: +1**. In the paranoid interpretation, successful heap corruption exploitation may affect kernel integrity.
* **Requires CAP_NET_ADMIN or equivalent in typical deployments: -1**. Full host administration may be required on strict systems, but delegated `CAP_NET_ADMIN`, container network administration, or reduced-capability service contexts can lower the practical privilege barrier.

Conservative score interpretation:

* Same core double-free and DoS signals apply.
* The conservative path assumes ordinary host `CAP_NET_ADMIN` is required and applies the stronger privilege penalty.
* Conservative score is therefore borderline/manual-review level rather than automatically Important.

## 3. Reachability analysis

The trigger is local control-plane access through the net shaper Generic Netlink operation, not packet data-plane traffic. It is not directly network reachable. In typical deployments, creating or changing network shaper state is expected to require `CAP_NET_ADMIN` or equivalent administrative permissions.

Namespaces and containers matter. If net shaper operations are available inside a delegated network namespace, container root or a service with reduced but meaningful network administration rights may be able to reach the vulnerable path without full host-root equivalence. This makes the paranoid `PR:L` style interpretation defensible for triage, while the conservative interpretation remains `PR:H` or admin-gated.

The affected subsystem is network control-plane functionality, not a universal packet-processing path. However, the described primitive is a direct kernel double free, so it should not be treated as a low-priority validation-only bug.

## 4. Severity interpretation

This behaves as **Actionable Moderate at minimum**, and as a **Strong Important candidate** under the paranoid but defensible interpretation.

The realistic demonstrated impact is local kernel memory corruption with likely crash or system instability. The theoretical risk is higher because double free bugs can sometimes be shaped into exploitable heap corruption and local privilege escalation, especially if an attacker can influence allocation timing and object reuse. The patch does not prove an arbitrary write or a working LPE chain, so the conservative score should not jump to Critical-like handling, but the explicit double free makes auto-close inappropriate.

## 5. One-sentence report phrase

A duplicate `NET_SHAPER_A_LEAVES` entry in a GROUP request can cause the same parent object to be queued twice for cleanup, leading to a kernel double free reachable through local Generic Netlink network-shaper control operations.

## 6. Manual review recommendation

**MANUAL CHECK REQUIRED**

Reason: the patch explicitly fixes a kernel double free, which is a real memory corruption primitive. Even though the path is local and usually `CAP_NET_ADMIN` gated, namespace delegation and reduced-capability network administration make the practical privilege boundary worth reviewing.

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

Patch: net: shaper: reject duplicate leaves in GROUP request [ Upstream
Commit: 5098b223f0f0c5c18a3884a8b0ea5bd4a0c7bd75
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=5098b223f0f0c5c18a3884a8b0ea5bd4a0c7bd75

Changed files:
  net/shaper/shaper.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=5098b223f0f0c5c18a3884a8b0ea5bd4a0c7bd75

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

The original Linux kernel CVE announcement for CVE-2026-64054 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64054

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:H/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: 4
  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: MODERATE
KPANIC detected for this report: YES
Published priority for this report (same as in Subject): MODERATE 7.0

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).