[CVE-2026-74737][MODERATE 7.0] net: ethernet: ti: am65-cpsw-nuss: Fix port_id extraction from SRC TAG [ Upstream

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

CVE: CVE-2026-74737
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: net: ethernet: ti: am65-cpsw-nuss: Fix port_id extraction from SRC TAG [ Upstream
Commit: 14fc40bf28390e0ebee6a072457c36b82c614100
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=14fc40bf28390e0ebee6a072457c36b82c614100
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74737
Analysis date: Wed, 26 Aug 2026 11:20:48 -0400
ActionableScore: 5
ActionableScore lower bound: 4
Actionable bucket: Actionable Moderate at minimum
Manual review required: YES

Summary:
A TI AM65 CPSW NUSS RX descriptor parsing bug can use hardware-reserved Source Tag bits as part of the MAC port ID, causing an invalid port lookup and OOB access that may be triggered from an adjacent network and crash the kernel.

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ABOUT THIS REPORT
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The original Linux kernel CVE announcement for CVE-2026-74737 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74737

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.

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AL-KERNEL CLASSIFICATION RESULT
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CVE-2026-74737	MODERATE	CHECK WITH IMPACT FROM ORIG NN IMPORTANT	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:A/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:H';CWE-129;CWE-125;*CWE-20;**CWE-476;Other CVSS 'AV:A/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '6.4';DESCR 'The TI AM65 CPSW NUSS RX path used the full 16 bit Source Tag from the RX DMA descriptor as a MAC port identifier even though only the lower 8 bits contain the real port ID. The upper 8 bits are hardware reserved and may contain arbitrary values, which can make the driver use an invalid port_id and access memory outside the valid port table. A network adjacent sender may trigger the RX path by sending traffic to the affected interface, but reliable triggering depends on the affected TI hardware and descriptor metadata behavior. For the CVSS the PR:N is used because no local account on the target is needed if the attacker can send L2 or adjacent network traffic to the device. Impact is at least denial of service via kernel crash. In the paranoid score, limited confidentiality or integrity impact is kept due to kernel OOB access, but there is no strong evidence of an arbitrary write primitive or reliable privilege escalation.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 5)	YES	REMOTE WRITE OOB DANGER SIMPLEFIX NETWORK DMAorINTERRUPT KERNEL_PANIC_PLUS_UAF HARDWARE LINUS KPANIC PACKET  KPANIC LOWERED_FROM_HIGH_BASED_ON_GUESSCVSS 	YES	NO	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=5
ActionableScoreLower=4

## 1. ActionableScore

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

## 2. Signal breakdown

Conservative scoring:

* Firmware-mediated external influence: +1
  The invalid `port_id` comes from RX DMA descriptor metadata where the upper 8 bits are hardware-reserved and arbitrary.
* Memory corruption, weak/indirect corruption candidate: +1
  The bug is an unchecked object index / invalid `port_id` used for port lookup, leading to out-of-bound access.
* Reliable kernel crash / strong DoS: +1
  The commit explicitly reports sporadic kernel crashes from the invalid `port_id`.
* Privileged kernel/device-management memory corruption path: +1
  The corruption occurs in a trusted Ethernet driver RX path using DMA descriptor metadata.

Paranoid delta:

* Network reachable / adjacent packet-triggered path: +2 instead of firmware-mediated +1
  A network-adjacent sender can exercise the RX path by sending traffic to the affected interface, although the exact invalid upper bits depend on hardware descriptor behavior.

Not awarded:

* No strong LPE plausibility. The patch does not show attacker-controlled reclaim, overwrite, callback control, type confusion, or arbitrary write.
* No strong generic memory corruption primitive. This is an invalid index / OOB access leading to crash, not a demonstrated OOB write.
* No confidentiality or integrity bonus in the main actionable score. Limited C/I was defensible for paranoid CVSS, but there is no clear read-back or write primitive for actionable scoring.

## 3. Reachability analysis

The bug is triggered in the TI AM65 CPSW NUSS Ethernet RX path. An attacker does not need a local account if they can send L2 or adjacent-network traffic to the affected interface, but reliable triggering depends on the affected TI hardware and how the RX DMA descriptor fills hardware-reserved Source Tag bits. This is not Internet-remote in the usual TCP/IP service sense and is best treated as adjacent-network plus hardware/DMA-mediated exposure.

Namespaces and containers do not meaningfully lower or raise the trigger requirement because the vulnerable path is packet reception in the host driver. The affected subsystem is hardware-specific, so exposure is not broad across all Linux systems, but for devices using this TI Ethernet driver the path is normal RX processing.

Call-site confidence: high. The provided context shows `port_id` being read from descriptor metadata, then passed to `am65_common_get_port(common, port_id)`, followed by dereference of `port->ndev`.

## 4. Severity interpretation

This behaves more like Actionable Moderate than ordinary Moderate because it is a packet RX path bug with OOB access and observed kernel crash. It is not a Strong Important candidate on the available evidence because attacker control over the invalid index is indirect and hardware-mediated, and the patch does not show a write primitive, UAF reclaim, object replacement, or privilege escalation path.

The theoretical risk is kernel memory misuse from an invalid port table access. The realistic demonstrated impact is denial of service through a sporadic kernel crash on affected TI hardware.

## 5. One-sentence report phrase

A TI AM65 CPSW NUSS RX descriptor parsing bug can use hardware-reserved Source Tag bits as part of the MAC port ID, causing an invalid port lookup and OOB access that may be triggered from an adjacent network and crash the kernel.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED

This should not be auto-closed because it is a network-adjacent Ethernet RX path OOB access with observed kernel crash potential, even though the current evidence supports DoS rather than a reliable privilege escalation primitive.

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

Patch: net: ethernet: ti: am65-cpsw-nuss: Fix port_id extraction from SRC TAG [ Upstream
Commit: 14fc40bf28390e0ebee6a072457c36b82c614100
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=14fc40bf28390e0ebee6a072457c36b82c614100

Changed files:
  drivers/net/ethernet/ti/am65-cpsw-nuss.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=14fc40bf28390e0ebee6a072457c36b82c614100

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

The original Linux kernel CVE announcement for CVE-2026-74737 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74737

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:A/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS vector: AV:A/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:H
  The Best / paranoid CVSS score: 6.4

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).