[CVE-2026-98322][MODERATE REGULAR] netfilter: nft_nat: fully initialise new_addr in netmap setup [ Upstream

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

CVE: CVE-2026-98322
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: netfilter: nft_nat: fully initialise new_addr in netmap setup [ Upstream
Commit: 29365695842db0a97b701a43a09fad1b4f7ecf3e
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=29365695842db0a97b701a43a09fad1b4f7ecf3e
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98322
Analysis date: Sat, 10 Oct 2026 02:53:52 -0400
ActionableScore: 0
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-2026-98322 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98322

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 REGULAR
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
======================================================================

CVE-2026-98322	MODERATE	https://www.kernelcve.org/list/?q=CVE-2026-98322 CHECK WITH IMPACT FROM ORIG NN MODERATE | AEGIS IMPACT MODERATE AEGIS_AS=0 LEGACY=MODERATE RESULT=SAME (legacy and Aegis reconciliation agree; DECISION: both MODERATE)	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H';*CWE-457;CWE-908;CWE-665;Other CVSS 'AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '5.9';DESCR 'An uninitialized value can reach nf_nat_setup_info because nft_nat_setup_netmap initializes only the 4 byte IPv4 member of a 16 byte stack union and then copies the complete union into both NAT address limits. A network packet can potentially exercise the affected evaluation path when a suitable IPv4 nftables netmap rule has already been configured, but creating that rule normally requires CAP_NET_ADMIN. For the CVSS the PR:N value represents a remote sender who only needs reachability to traffic processed by the existing rule. AC:H reflects the required nondefault netmap configuration and packet path. The demonstrated result is a KMSAN uninitialized value report with possible limited availability impact. There is no demonstrated UAF, OOB access, information disclosure, or controlled write. A kernel crash is mainly plausible on diagnostic systems that convert warnings into panics.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 0)	MAYBE	REMOTE READ KASAN OOB INIT SIMPLEFIX NETFILTER LINUS IPV6  DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN4	-	-	checked

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

ActionableScore=0
PrimitiveClass=CLASS_C
RealUAF=NO
HostAdminRequired=UNKNOWN
NamespaceScopedPrivilege=UNKNOWN
ImportantCandidate=NO
ManualReview=RECOMMENDED
AutoDowngradeAllowed=YES
RequiresHostUID0=UNKNOWN
AuthorizationDecisionBypass=NO
ProtectedResourceImpact=NONE
B4PendingReview=NO
B4PendingConfirmed=NO

1. ActionableScore

* Raw conservative score: 0.
* Conservative score: 0.
* Raw paranoid score: 0.
* Paranoid score: 0.
* No floor or cap was applied.
* Final recommended bucket: **Ordinary Moderate**::

2. Signal breakdown

* +1 Weak or indirect invalid-state consumption. Twelve uninitialized stack bytes are copied into `nf_nat_range2` address fields and reach `nf_nat_setup_info()`.
* -1 Highly constrained internal state. The destination is fixed, the copied bytes are not attacker-controlled, and no OOB access, disclosure, write outside the intended object, authorization bypass, or control-flow effect is established.
* No remote-reachability points. Packet processing may reach `nft_nat_eval()`, but a suitable IPv4 netmap rule must already exist and the evidence does not establish an attacker-controlled complete trigger without privileged setup.
* No crash point. The demonstrated result is a KMSAN uninitialized-value report, not a production kernel panic. A diagnostic warning-to-panic configuration is insufficient for an additional score.
* No confidentiality or integrity points. No path copies the stack bytes to userspace or the network, and no unauthorized modification is demonstrated.
* NEW52 B5-R does not apply. There is no heap OOB write, retry-accumulated index, or later consumption of corrupted out-of-bounds storage.
* NEW53 B3-PENDING does not apply. No shared or file-backed storage write is involved.
* NEW54 B4-PENDING does not apply. No authorization decision or mandatory security guard is changed.
* Controlled corruption, arbitrary write, UAF, controlled reclaim, LPE, and persistent resource exhaustion are not demonstrated.

3. Reachability analysis

The vulnerable function is evaluated in an nftables NAT packet path after an IPv4 netmap rule has been installed. Creating such a rule normally involves `CAP_NET_ADMIN`, but the supplied evidence does not establish whether the security-relevant trigger requires the same actor to install the rule or whether an external packet sender can independently trigger the report after prior configuration.

The governing capability namespace and the completeness of a namespace-only trigger are not shown. Therefore `HostAdminRequired` and `NamespaceScopedPrivilege` remain `UNKNOWN`. No special hardware, boot option, race, retry sequence, or attacker-controlled allocation pattern is involved.

4. Primitive and severity interpretation

The exact defect is incomplete initialization of an on-stack `union nf_inet_addr`. The IPv4 path initializes four bytes and copies the complete sixteen-byte union into two correctly sized destination fields. This is not an OOB read or write because both source and destination objects have the full union size.

The upper bytes carry indeterminate kernel stack data into internal NAT state, and KMSAN observes their later consumption by `nf_nat_setup_info()`. No external disclosure or security-sensitive influence of those bytes is established. The issue is therefore `CLASS_C` invalid-state behavior rather than a memory-corruption primitive.

There is no lifetime violation, repeated release, shared-backing write, or authorization bypass. The patch-supported consequence is a sanitizer report. A production crash or NAT behavior change remains unproven. `ImportantCandidate=NO` because there is no Important-preserving primitive, and `AutoDowngradeAllowed=YES` because no unresolved corruption or security-boundary leverage would be lost.

5. One-sentence report phrase

An IPv4 nftables netmap operation copies twelve uninitialized stack bytes into internal NAT range fields, but the supplied evidence establishes only a KMSAN invalid-value report and no OOB access, disclosure, controlled corruption, or authorization bypass.

6. Manual review recommendation

MANUAL CHECK RECOMMENDED

Confirm whether any IPv4 `nf_nat_setup_info()` descendant consumes the upper twelve bytes in a security-relevant comparison, hash, copy, or externally observable result. Current evidence supports automatic downgrade if no such consumer exists.

7. Call-site confidence

Call-site confidence: medium

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

Patch: netfilter: nft_nat: fully initialise new_addr in netmap setup [ Upstream
Commit: 29365695842db0a97b701a43a09fad1b4f7ecf3e
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=29365695842db0a97b701a43a09fad1b4f7ecf3e

Changed files:
  net/netfilter/nft_nat.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=29365695842db0a97b701a43a09fad1b4f7ecf3e

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

The original Linux kernel CVE announcement for CVE-2026-98322 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98322

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:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L
  The Best / paranoid CVSS vector: AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS score: 5.9

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: 0

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: NO
Published priority for this report (same as in Subject): MODERATE REGULAR

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).