[CVE-2026-64125][MODERATE 7.0] net: bcmgenet: keep RBUF EEE/PM disabled

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

CVE: CVE-2026-64125
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: net: bcmgenet: keep RBUF EEE/PM disabled
Commit: 2040eb83f6ada148fb32dd98b943a498005d79f2
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=2040eb83f6ada148fb32dd98b943a498005d79f2
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64125
Analysis date: Sun, 19 Jul 2026 18:44:36 -0400
ActionableScore: 5
ActionableScore lower bound: 3
Actionable bucket: Actionable Moderate at minimum
Manual review required: YES

Summary:
Broadcom GENET RBUF EEE/PM enablement can break RX forwarding after EEE/LPI activity, causing persistent RX denial of service and on some boards a kernel paging fault in `skb_release_data`, with exploitation most plausibly limited to adjacent-network conditions on affected hardware.

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

The original Linux kernel CVE announcement for CVE-2026-64125 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64125

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-2026-64125	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-754;CWE-703;CWE-693;Other CVSS 'AV:A/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '6.4';DESCR 'Broadcom GENET RBUF EEE and PM enablement can break the RX path once MAC EEE becomes active or when the link exits LPI. The link may remain up while received frames stop reaching DMA, causing RX traffic loss and denial of service. On some boards the same condition was observed as a paging fault in skb_release_data through bcmgenet_rx_poll, so the worst grounded interpretation includes possible limited memory corruption impact rather than only a clean receive stall. For the CVSS the PR:N is used because an attacker does not need local privileges on the target if the affected Ethernet interface is reachable from the same L2 network and EEE conditions can be induced by traffic and link activity. The attack is not Internet routable in the usual sense and is best treated as adjacent network exposure. Impact is primarily denial of service, with limited confidentiality or integrity impact kept only for the paranoid score because the crash signature suggests corrupted RX or SKB state but does not demonstrate a reliable privilege escalation primitive.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 4)	YES	REMOTE DANGER NETWORK KERNEL_PANIC_PLUS_UAF HARDWARE LINUS  LOWERED_FROM_HIGH_BASED_ON_GUESSCVSS  DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5	NO	NO	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=5
ActionableScoreLower=3

## 1. ActionableScore

* Conservative score: 3
* Paranoid score: 5
* Final recommended bucket: **Actionable Moderate at minimum**::

## 2. Signal breakdown

Conservative scoring:

* Firmware-mediated external influence: +1
  The trigger depends on GENET hardware, PHY EEE/LPI behavior, and RBUF EEE/PM state rather than a pure software packet parser.
* Reliable kernel crash / strong DoS: +1
  The commit describes RX traffic stopping while link remains up, and on some boards a paging fault occurs in `skb_release_data` via `bcmgenet_rx_poll`.
* Availability impact realistic: +1
  RX path failure can persist as a functional network outage until reset or driver recovery.
* Physical-only or rare hardware-only condition: -1
  The issue is limited to Broadcom GENET platforms with affected EEE behavior, not a generic networking core path.

Paranoid scoring:

* Adjacent-network triggerability: +2
  A same-L2 attacker may influence traffic and link-idle/LPI behavior when the affected Ethernet interface is reachable, although this is not Internet-routable.
* Weak/indirect corruption candidate: +1
  The paging fault in `skb_release_data` suggests corrupted RX/SKB state, but the patch does not show UAF reclaim, OOB write, type confusion, or attacker-controlled overwrite.
* Reliable kernel crash / strong DoS: +1
  Crash signature is explicitly reported on affected boards.
* Privileged kernel/device/DMA-adjacent state corruption path: +1
  The failure occurs in a NIC RX path involving RBUF to DMA forwarding and SKB release handling.
* Hardware-specific condition: -1
  Exploitability depends on specific GENET hardware and EEE/LPI behavior.

## 3. Reachability analysis

The most realistic attacker is adjacent to the affected Ethernet segment, not a remote Internet attacker. No local privileges on the target are required if the attacker can influence traffic or link-idle behavior enough to exercise EEE/LPI transitions. The path may become more exposed because EEE can be enabled by default through `phy_support_eee()`, but the bug remains hardware-specific to affected Broadcom GENET platforms such as BCM2711 or related 4908-family boards.

Namespaces and containers do not materially change the main trigger model because the relevant path is NIC hardware RX behavior, not a local namespace-controlled API. Local administrative control through `ethtool` can also enable TX LPI on older kernels, but that is not the only plausible exposure.

## 4. Severity interpretation

This is stronger than an ordinary low-risk hardware quirk because it can cause RX loss and has a reported kernel paging fault in `skb_release_data`. However, it is not a Strong Important candidate on current evidence because the patch does not demonstrate a controllable memory corruption primitive, attacker-controlled reclaim, arbitrary write, type confusion, or privilege escalation path.

Realistic impact is primarily adjacent-network denial of service on affected hardware. The paranoid score keeps it as Actionable Moderate because the crash occurs in SKB release handling and deserves manual review, but the available evidence does not justify treating it as a likely LPE or remote code execution issue.

## 5. One-sentence report phrase

Broadcom GENET RBUF EEE/PM enablement can break RX forwarding after EEE/LPI activity, causing persistent RX denial of service and on some boards a kernel paging fault in `skb_release_data`, with exploitation most plausibly limited to adjacent-network conditions on affected hardware.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED

The issue is adjacent-network reachable on affected systems and includes a crash in an SKB release path, but the exploitability beyond DoS is not proven. Manual review should focus on whether the `skb_release_data` paging fault reflects only corrupted driver state or a reusable SKB/RX lifetime corruption primitive.

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

Patch: net: bcmgenet: keep RBUF EEE/PM disabled
Commit: 2040eb83f6ada148fb32dd98b943a498005d79f2
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=2040eb83f6ada148fb32dd98b943a498005d79f2

Commit description:

Setting RBUF_EEE_EN | RBUF_PM_EN in RBUF_ENERGY_CTRL breaks the RX
path on GENET hardware once MAC EEE becomes active. RX traffic stops
flowing while the link stays up and the usual descriptor/RX error
counters remain quiet. In that state the MAC still accepts frames
(rbuf_ovflow_cnt keeps climbing) but RBUF no longer forwards them to
DMA, so rx_packets is no longer incremented at the netdev level. On
some boards the corruption ends up as a paging fault in
skb_release_data via bcmgenet_rx_poll on an LPI exit.

Reproduced on Pi 4B (BCM2711 + BCM54213PE) and confirmed by Florian
Fainelli on an internal Broadcom 4908-family board with the same crash
signature. RBUF_PM_EN is not publicly documented.

This shows up more often now that phy_support_eee() enables EEE by
default, but it also affects older kernels as soon as TX LPI is
turned on via ethtool, so it is not specific to recent changes.

Always clear RBUF_EEE_EN | RBUF_PM_EN in bcmgenet_eee_enable_set so
the bits stay off across resets. UMAC and TBUF setup is left alone so
TX-side EEE keeps working.

Link: raspberrypi/linux#7304
Fixes: 6ef398e ("net: bcmgenet: add EEE support")
Cc: stable@vger.kernel.org
Signed-off-by: Nicolai Buchwitz <nb@tipi-net.de>
Reviewed-by: Florian Fainelli <florian.fainelli@broadcom.com>
Link: https://patch.msgid.link/20260520184320.652053-1-nb@tipi-net.de
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  drivers/net/ethernet/broadcom/genet/bcmgenet.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=2040eb83f6ada148fb32dd98b943a498005d79f2

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

The original Linux kernel CVE announcement for CVE-2026-64125 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64125

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: 3
  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: NO
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).