[CVE-2026-98022][MODERATE REGULAR] net: cap tx_queue_len at S16_MAX to prevent oversized ring allocations [ Upstream

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

CVE: CVE-2026-98022
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: net: cap tx_queue_len at S16_MAX to prevent oversized ring allocations [ Upstream
Commit: 81c0e02076989743a603806a5a4f44d2c40dc01f
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=81c0e02076989743a603806a5a4f44d2c40dc01f
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98022
Analysis date: Sat, 26 Sep 2026 14:32:01 -0400
ActionableScore: 3
ActionableScore lower bound: unknown
Actionable bucket: Ordinary Moderate
Manual review required: NO

Summary:
No one-sentence report phrase was found.

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

The original Linux kernel CVE announcement for CVE-2026-98022 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98022

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-2026-98022	MODERATE	https://www.kernelcve.org/list/?q=CVE-2026-98022 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:N/I:N/A:H';**CWE-400;CWE-770;CWE-789;BEST CVSS score: '5.5';DESCR 'An unprivileged local user can set an excessively large tx_queue_len inside a new user and network namespace. Several networking subsystems use this value to size skb_array or ptr_ring allocations. Repeated creation or reconfiguration of veth tun or tap devices can exhaust global memory and trigger an OOM condition. For the CVSS the PR:L metric is used because exploitation requires local code execution and the ability to create a user and network namespace. The issue is not network reachable through packet traffic. Impact is denial of service only. Confidentiality and integrity impact are not supported because the patch indicates resource exhaustion without a memory corruption or information disclosure primitive.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 3)	YES	REMOTE DANGER HARDWARE LINUS TEST QDISC 	NO	NO	checked

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

ActionableScore=3
PrimitiveClass=NONE
RealUAF=NO
HostAdminRequired=NO
NamespaceScopedPrivilege=YES
ImportantCandidate=NO
ManualReview=NO
AutoDowngradeAllowed=YES

1. ActionableScore

* Raw conservative score: 3
* Conservative score: 3
* Raw paranoid score: 3
* Paranoid score: 3
* Final recommended bucket: **Ordinary Moderate**::

2. Signal breakdown

* +1 Local unprivileged trigger. The supplied reproducer establishes that an unprivileged local user can create a fresh user and network namespace with unshare -Urn and perform the complete vulnerable configuration sequence.
* +1 Strong denial of service. Repeated veth, tun, or tap allocation operations with an oversized tx_queue_len can exhaust memory and induce an OOM condition in the affected system or guest.
* +1 Cross-boundary isolation impact. Resource consumption is described as global memory exhaustion even though the attacker operates through a newly created user and network namespace. This can affect workloads outside the attacker namespace when memory cgroup limits do not contain the allocations.

Important non-awarded signals:

* +0 Memory corruption. No UAF, OOB access, stale pointer, arbitrary write, refcount corruption, or invalid lifetime operation is established.
* +0 Confidentiality and integrity. The supplied patch and reproducer establish resource exhaustion only. They do not establish disclosure, cross-namespace data access, or unauthorized modification.
* +0 Remote reachability. The vulnerable operation is a local network control-plane configuration path and is not reachable through ordinary packet traffic.
* +0 Broad default exposure. CONFIG_NET_SCHED, CONFIG_VETH, CONFIG_USER_NS, and CONFIG_NET_NS are required. These are common in many container-oriented deployments, but the evidence does not establish universal default exposure.
* +0 Persistent resource leak. The bug causes attacker-driven oversized allocations, not a missing-release or unrecoverable reference leak.
* +0 Additional paranoid escalation. The demonstrated primitive and consequence are already captured by local cross-namespace resource exhaustion. There is no technically supported stronger corruption or boundary-bypass primitive.

3. Reachability analysis

An ordinary local user can trigger the issue where unprivileged user namespaces are enabled and the required networking configuration options are present. The supplied reproducer positively establishes the complete sequence through a newly created user and network namespace: create namespace, gain namespace-scoped capabilities, create namespace-local networking objects, set a large tx_queue_len, and cause affected ring allocations.

The relevant CAP_NET_ADMIN checks for namespace-local veth, qdisc, tun, and tap configuration are reachable in the attacker-created network namespace. The pfifo_fast plus veth path alone is sufficient according to the supplied reproduction conditions. Therefore NamespaceScopedPrivilege is YES and HostAdminRequired is NO.

No prior host-admin setup is identified beyond kernel configuration and the distribution policy permitting unprivileged user namespaces. No special hardware, firmware interaction, narrow race, or attacker-controlled packet path is required. The allocation sequence is repeatable and deterministic, but repeatability is not scored separately because it is part of the demonstrated resource-exhaustion consequence.

Memory cgroups or container limits can mitigate host-wide impact in some deployments. They do not remove the underlying issue where allocations are charged to globally available memory rather than being safely bounded by tx_queue_len validation.

4. Primitive and severity interpretation

The exact primitive is unbounded attacker-controlled resource allocation. The tx_queue_len field is accepted with a very large value and is later used as a ring-size multiplier by pfifo_fast, tun, and tap paths. This permits repeated allocation of skb_array or ptr_ring storage until memory exhaustion occurs.

This is not an active-object lifetime bug, UAF, stale-object access, ownership violation, authorization bypass, or semantic reinterpretation issue. No first lifetime operation, second release, refcount mutation, controlled reclaim, callback use, arbitrary write, disclosure path, or integrity primitive exists in the supplied evidence.

PrimitiveClass is NONE because the patch establishes only an insufficient bound on a resource-sizing input. The demonstrated consequence is local denial of service through OOM pressure. A host-wide or cross-container impact is plausible when cgroup limits do not constrain the attacker namespace, but this remains a resource-exhaustion consequence rather than a privilege-escalation or memory-corruption primitive.

ImportantCandidate is NO because no concrete corruption, ownership, lifetime, authorization, or security-boundary access primitive remains unresolved. AutoDowngradeAllowed is YES because the issue is a well-characterized local resource-exhaustion condition with a bounded and direct fix, and it does not require manual exploitability analysis.

Likely operational severity is ordinary Moderate. It should be patched on multi-tenant systems, CI workers, container hosts, and systems that permit unprivileged user namespaces without effective memory cgroup containment. It does not justify Important classification from the supplied evidence.

5. One-sentence report phrase

An unprivileged local user can use a user and network namespace to configure an oversized tx_queue_len and force excessive networking ring allocations, causing global memory exhaustion and denial of service.

6. Manual review recommendation

NO MANUAL CHECK NEEDED

The issue is a directly demonstrated and repeatable local resource-exhaustion condition without a memory-corruption, lifetime, authorization-bypass, confidentiality, integrity, or privilege-escalation primitive.

7. Call-site confidence

Call-site confidence: high

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

Patch: net: cap tx_queue_len at S16_MAX to prevent oversized ring allocations [ Upstream
Commit: 81c0e02076989743a603806a5a4f44d2c40dc01f
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=81c0e02076989743a603806a5a4f44d2c40dc01f

Changed files:
  net/core/dev.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=81c0e02076989743a603806a5a4f44d2c40dc01f

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

The original Linux kernel CVE announcement for CVE-2026-98022 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98022

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: Not available
  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: unknown
  Paranoid ActionableScore: 3

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).