[CVE-2026-98321][LOW] netfilter: nf_nat: unregister and release hooks on error [ Upstream

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

CVE: CVE-2026-98321
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: netfilter: nf_nat: unregister and release hooks on error [ Upstream
Commit: 79084567cd082fb4482e1ea457580e7d6504dd99
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=79084567cd082fb4482e1ea457580e7d6504dd99
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98321
Analysis date: Sat, 10 Oct 2026 02:44:00 -0400
ActionableScore: 1
ActionableScore lower bound: unknown
Actionable bucket: Ordinary Moderate
Manual review required: NO

Summary:
No one-sentence report phrase was found.

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

The original Linux kernel CVE announcement for CVE-2026-98321 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98321

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.

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

CVE-2026-98321	LOW	https://www.kernelcve.org/list/?q=CVE-2026-98321 CHECK WITH IMPACT FROM ORIG NN LOW | AEGIS IMPACT LOW AEGIS_AS=1 LEGACY=LOW RESULT=SAME (legacy and Aegis reconciliation agree; DECISION: both LOW)	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:L';*CWE-401;*CWE-772;CWE-459;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '2.5';DESCR 'A failure in nf_hook_entries_insert_raw can leave newly registered NAT hooks and their private allocations referenced after nf_nat_register_fn returns an error. The demonstrated primitive is persistent resource retention rather than memory corruption, and the available patch context does not establish reliable host wide memory exhaustion. For the CVSS the PR:L in the paranoid score reflects environments where CAP_NET_ADMIN or network namespace administration is delegated to a container root or restricted service account. The normal host configuration path is more privileged and is represented by PR:H in the base score. AC:H applies because an attacker must reach the specific insertion failure path, which normally depends on an allocation or similar internal failure rather than ordinary ruleset activity. The issue is not directly reachable through network packets. Impact is limited to low availability degradation from retained kernel resources, with no supported confidentiality or integrity impact.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 1)	MAYBE	REMOTE LOCK INIT NETFILTER LEAK ERRORPATH LINUS 	-	-	checked

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

ActionableScore=1
PrimitiveClass=NONE
RealUAF=NO
HostAdminRequired=UNKNOWN
NamespaceScopedPrivilege=UNKNOWN
ImportantCandidate=NO
ManualReview=NO
AutoDowngradeAllowed=YES
RequiresHostUID0=UNKNOWN
AuthorizationDecisionBypass=NO
ProtectedResourceImpact=NONE
B4PendingReview=NO
B4PendingConfirmed=NO

1. ActionableScore

* Raw conservative score: 1
* Conservative score: 1
* Raw paranoid score: 1
* Paranoid score: 1
* No floor or cap was applied.
* Final recommended bucket: **Ordinary Moderate**::

2. Signal breakdown

Positive signals:

* +1 Concrete persistent kernel resource/reference leak. After successful registration, failure in `nf_hook_entries_insert_raw()` leaves the newly registered NAT hooks and associated `nat_ops` and private allocations unreleased.

Negative signals:

* No negative points. The unavailable caller and privilege details are uncertainty, not evidence for a privilege or exposure penalty.

Important non-awarded signals:

* No UAF, double release, OOB access, arbitrary write, or active-object corruption is established.
* No reliable kernel crash or host-wide resource exhaustion is demonstrated.
* Repeated accumulation under attacker control is not established.
* Remote reachability is not established. Network packets do not directly invoke this registration error path.
* B5-R does not apply because there is no heap OOB write, retry-accumulated offset, or later consumption of corrupted state.
* B3-PENDING does not apply because no shared-backing write is present.
* Authorization bypass and B4-PENDING do not apply.
* Confidentiality, integrity, LPE, and extra availability points were not awarded.

Arithmetic:

* Conservative: persistent resource leak +1 = 1.
* Paranoid: persistent resource leak +1 = 1.
* No defensible paranoid bonus exists without evidence of repeatable accumulation or meaningful exhaustion.

3. Reachability analysis

The vulnerable operation is an internal NAT-hook registration path followed by failure of `nf_hook_entries_insert_raw()`. The supplied patch does not show the userspace caller, capability check, or a complete method for reliably forcing this insertion failure.

NAT configuration commonly involves `CAP_NET_ADMIN`, but the evidence does not establish whether the complete trigger requires host-level authority or can be performed entirely within an attacker-created network namespace. Therefore, `HostAdminRequired` and `NamespaceScopedPrivilege` remain `UNKNOWN`, with no privilege penalty or unprivileged-trigger bonus.

No prior host setup, sysctl, boot option, special hardware, or direct packet-triggered path is established. This is not a race. The main trigger limitation is the need to reach the specific insertion-error branch, potentially through allocation failure, without evidence that an attacker can reliably repeat it.

4. Primitive and severity interpretation

The exact primitive is retention of registered hooks and their associated allocations after a registration sequence fails. It is a concrete resource-management defect, but not memory corruption or post-lifetime use.

There is no stale dereference, no second release or refcount mutation, and no active structured object consumed after free. The patch instead adds rollback that unregisters newly installed hooks before releasing their allocations.

`PrimitiveClass=NONE` is appropriate because no corruption, UAF, ownership violation, authorization bypass, or independently useful security primitive is established. The demonstrated consequence is a kernel memory leak. Host-wide exhaustion is speculative because attacker-controlled repetition and meaningful accumulation are not shown.

`ImportantCandidate=NO` and `AutoDowngradeAllowed=YES` follow from the absence of an Important-preserving primitive. Operational severity is Low-like unless additional evidence demonstrates reliable repeated leakage sufficient to exhaust host memory.

5. One-sentence report phrase

Failure to insert an NF NAT hook can leave newly registered hooks and private allocations unreleased, causing a limited kernel memory leak without demonstrated memory corruption, reliable host-wide exhaustion, or direct network reachability.

6. Manual review recommendation

NO MANUAL CHECK NEEDED

The patch establishes only a cleanup-related resource leak, with no evidence of corruption, security-boundary bypass, reliable crash, or attacker-controlled accumulation.

7. Call-site confidence

Call-site confidence: medium

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

Patch: netfilter: nf_nat: unregister and release hooks on error [ Upstream
Commit: 79084567cd082fb4482e1ea457580e7d6504dd99
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=79084567cd082fb4482e1ea457580e7d6504dd99

Changed files:
  net/netfilter/nf_nat_core.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=79084567cd082fb4482e1ea457580e7d6504dd99

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

The original Linux kernel CVE announcement for CVE-2026-98321 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98321

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:L
  The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:L
  The Best / paranoid CVSS score: 2.5

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: unknown
  Paranoid ActionableScore: 1

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).