[CVE-2026-46324][MODERATE 7.0] netfilter: nf_tables: use list_del_rcu for netlink hooks [ Upstream

[CVE-2026-46324][MODERATE 7.0] netfilter: nf_tables: use list_del_rcu for netlink hooks [ Upstream

[AL-KERNEL]

CVE: CVE-2026-46324
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: netfilter: nf_tables: use list_del_rcu for netlink hooks [ Upstream
Commit: 0bd93ce4f3c35e845532184331d7917d7e562c80
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=0bd93ce4f3c35e845532184331d7917d7e562c80
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46324
Analysis date: Tue, 09 Jun 2026 09:08:36 -0400
ActionableScore: 5
ActionableScore lower bound: 4
Actionable bucket: Actionable Moderate at minimum
Manual review required: YES

Summary:
An unsafe list_del on nf_tables netdev and flowtable hook lists can race with RCU netlink dumpers and expose stale or inconsistent hook entries, creating a local kernel crash risk that should not be auto-closed.

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

The original Linux kernel CVE announcement for CVE-2026-46324 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46324

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.

======================================================================
AL-KERNEL CLASSIFICATION RESULT
======================================================================

CVE-2026-46324	MODERATE	CHECK	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-362;*CWE-416;CWE-667;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '7';DESCR 'nf_tables netdev and flowtable hook lists can be walked by concurrent netlink dumpers while control plane code unregisters and removes hooks. Some unregister paths used list_del instead of list_del_rcu, which is unsafe for RCU protected traversal and can expose a concurrent reader to inconsistent list pointers or a stale hook entry. The realistic impact is a local denial of service through kernel crash or hang during nftables hook removal and dump activity. In the paranoid interpretation this is treated as an RCU list race with a possible use after free style memory safety consequence, so confidentiality and integrity impact are kept high for manual review sensitivity. For the CVSS the PR:L is used for the paranoid score because CAP_NET_ADMIN may be available to a less trusted local actor in a user namespace, container, or delegated network administration context. The issue is not directly network reachable and is triggered through nftables control plane operations rather than packet traffic.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 5)	YES	REMOTE INIT SIMPLEFIX NETFILTER KPANIC 	NO	NO	checked

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

ActionableScore=5
ActionableScoreLower=4

## 1. ActionableScore

* Conservative score: 4
* Paranoid score: 5
* Final recommended bucket: **Actionable Moderate at minimum**::

## 2. Signal breakdown

Conservative scoring:

* Local unprivileged or delegated trigger: +1
  The modifying path normally needs CAP_NET_ADMIN, but nftables operations may be reachable by less trusted actors in user namespaces, containers, or delegated network administration contexts.

* Memory corruption, weak or indirect corruption candidate: +1
  The bug is an unsafe list_del on a list that can be traversed by RCU netlink dumpers. This can expose readers to inconsistent list pointers or stale hook entries.

* Real lifetime or RCU corruption: +1
  The object is freed through RCU, but the unlink operation must also be RCU safe. Using list_del instead of list_del_rcu breaks the expected RCU list traversal semantics.

* Reliable kernel crash or strong DoS concern: +1
  A concurrent dumper can observe a corrupted list state and plausibly trigger a crash or hang.

* Broad subsystem exposure: +1
  nf_tables is a common kernel networking control-plane subsystem.

* Hard race or timing dependency: -1
  Triggering requires overlap between hook unregister or destruction and concurrent netlink dumping.

Paranoid adjustment:

* Paranoid memory corruption interpretation: +1 additional
  Treat the unsafe RCU list deletion in netfilter as a generic RCU memory safety candidate rather than only a weak corruption candidate. This raises the score from 4 to 5, but does not justify LPE by itself.

Not counted:

* Remote reachable: +0
  This is not packet-triggered and not directly reachable over the network.

* Strong LPE plausibility: +0
  No attacker-controlled reclaim, overwrite, callback dispatch, type confusion, or refcount takeover is shown.

* Confidentiality or integrity impact: +0 conservative
  The patch supports crash or memory safety concern, but not a demonstrated read/write primitive.

## 3. Reachability analysis

The realistic trigger is local nftables control-plane activity that unregisters or destroys netdev or flowtable hooks while another task performs a netlink dump over the same RCU-protected lists. In typical host deployments, modifying these objects requires CAP_NET_ADMIN, which lowers conservative exploitability. In containerized or user namespace configurations, CAP_NET_ADMIN may be delegated to a less trusted local actor, so the paranoid interpretation uses a lower practical privilege barrier.

The path is not a remote packet-processing path. Network traffic alone should not trigger it. Exploitation requires control-plane operations and a race with dump activity.

## 4. Severity interpretation

This is more than an ordinary low-risk cleanup because it fixes incorrect RCU list deletion in netfilter, a memory-lifetime-sensitive subsystem. Realistically, it behaves like a local DoS or crash bug caused by concurrent list traversal and removal.

Theoretical memory corruption potential exists because RCU readers may observe stale or inconsistent list state. However, the patch does not show a strong exploit primitive such as attacker-controlled reuse, arbitrary write, callback hijack, type confusion, or refcount takeover. Therefore it is best treated as Actionable Moderate, not a clear Important vulnerability.

## 5. One-sentence report phrase

An unsafe list_del on nf_tables netdev and flowtable hook lists can race with RCU netlink dumpers and expose stale or inconsistent hook entries, creating a local kernel crash risk that should not be auto-closed.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED

This is an RCU list race in netfilter with a plausible memory safety consequence. Even though current evidence mainly supports local DoS, the affected pattern is dangerous enough to require manual review rather than automatic closure.

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

Patch: netfilter: nf_tables: use list_del_rcu for netlink hooks [ Upstream
Commit: 0bd93ce4f3c35e845532184331d7917d7e562c80
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=0bd93ce4f3c35e845532184331d7917d7e562c80

Changed files:
  net/netfilter/nf_tables_api.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=0bd93ce4f3c35e845532184331d7917d7e562c80

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

The original Linux kernel CVE announcement for CVE-2026-46324 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46324

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:H/UI:N/S:U/C:N/I:N/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: 4
  Paranoid ActionableScore: 5

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).