[CVE-2026-46188][MODERATE REGULAR] octeon_ep_vf: add NULL check for napi_build_skb() [ Upstream

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

CVE: CVE-2026-46188
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: octeon_ep_vf: add NULL check for napi_build_skb() [ Upstream
Commit: 60246cdd4c515ea7d920cddf48932efcb990773e
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=60246cdd4c515ea7d920cddf48932efcb990773e
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46188
Analysis date: Thu, 28 May 2026 06:32:22 -0400
ActionableScore: 2
ActionableScore lower bound: unknown
Actionable bucket: Ordinary Moderate / Low-like
Manual review required: NO

Summary:
Incoming traffic on an affected `octeon_ep_vf` interface can hit an unchecked `napi_build_skb()` allocation failure and trigger a NULL pointer dereference, causing a kernel DoS under memory pressure.

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

The original Linux kernel CVE announcement for CVE-2026-46188 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46188

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-2026-46188	MODERATE	CHECK	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-476;CWE-252;CWE-754;BEST CVSS score: '5.9';DESCR 'octeon_ep_vf RX processing used the result of napi_build_skb() without checking for NULL in both single buffer and multi fragment receive paths. Under allocation failure, incoming traffic can reach skb_reserve() or related skb handling with a NULL skb and crash the kernel. For the CVSS the PR:N is used for the paranoid score because the attacker does not need local privileges if traffic can reach the affected VF interface, although triggering depends on memory pressure and the specific octeon_ep_vf hardware path. The issue is network reachable through packet receive processing but has AC:H due to the allocation failure condition. Impact is denial of service only, with no evidence of information disclosure, integrity impact, or privilege escalation.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like (with actual score 2)	YES	REMOTE NULLPTR NETWORK SKB LINUS MEMORY  DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5	YES	NO	checked

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

ActionableScore=2

## 1. ActionableScore

* Conservative score: **2**
* Paranoid score: **2**
* Final recommended bucket: **Ordinary Moderate / Low-like**::

## 2. Signal breakdown

* **Remote reachable / network-triggerable: +2**
  The vulnerable code is in the RX path of `octeon_ep_vf`, so incoming packets can reach the affected processing path if the VF interface is exposed.

* **Reliable kernel crash / strong DoS: +1**
  If `napi_build_skb()` returns `NULL`, the old code dereferences the NULL `skb`, leading to a kernel crash.

* **Hard or unreliable condition: -1**
  The crash requires allocation failure in `napi_build_skb()`, typically memory pressure or allocator failure timing, not just a normal packet.

* **Rare AND difficult-to-reach subsystem/configuration: -1**
  The issue is limited to systems using the Marvell Octeon EP VF driver. This is not a broad default network stack path.

No UAF, OOB write, arbitrary write, information leak, integrity impact, or privilege escalation primitive is shown.

## 3. Reachability analysis

An attacker may influence the RX path by sending traffic to an affected `octeon_ep_vf` interface. No local privileges are needed if the interface is reachable over the network. However, reliable triggering also requires `napi_build_skb()` allocation failure, so exploitation depends on memory pressure and the specific hardware or VF deployment. Containers do not materially change the remote packet reachability, but the affected driver must be present and active.

## 4. Severity interpretation

This behaves like a remote or adjacent packet-triggered DoS under memory pressure, not like an Important-class memory corruption issue. The realistic impact is kernel crash from NULL pointer dereference. There is no evidence of confidentiality impact, integrity impact, or privilege escalation.

## 5. One-sentence report phrase

Incoming traffic on an affected `octeon_ep_vf` interface can hit an unchecked `napi_build_skb()` allocation failure and trigger a NULL pointer dereference, causing a kernel DoS under memory pressure.

## 6. Manual review recommendation

**MANUAL CHECK RECOMMENDED**

The primitive is only NULL dereference, but the path is network RX processing, so it should receive at least lightweight manual review before autoclose.

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

Patch: octeon_ep_vf: add NULL check for napi_build_skb() [ Upstream
Commit: 60246cdd4c515ea7d920cddf48932efcb990773e
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=60246cdd4c515ea7d920cddf48932efcb990773e

Changed files:
  drivers/net/ethernet/marvell/octeon_ep_vf/octep_vf_rx.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=60246cdd4c515ea7d920cddf48932efcb990773e

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

The original Linux kernel CVE announcement for CVE-2026-46188 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46188

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: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: 2

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).