* [CVE-2026-98574][MODERATE 7.0] net: bcmgenet: stop Tx NAPI before disabling the queues [ Upstream
@ 2026-10-24 12:37 21% AL-KERNEL
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From: AL-KERNEL @ 2026-10-24 12:37 UTC (permalink / raw)
To: kernel-cve
CVE: CVE-2026-98574
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: net: bcmgenet: stop Tx NAPI before disabling the queues [ Upstream
Commit: 63bcc2fee6419963e45e7c2cd698fa862409601d
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=63bcc2fee6419963e45e7c2cd698fa862409601d
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98574
Analysis date: Sat, 24 Oct 2026 08:37:37 -0400
ActionableScore: 3
ActionableScore lower bound: unknown
Actionable bucket: Borderline / manual review recommended
Manual review required: YES
Summary:
A suspend/shutdown ordering race permits `bcmgenet_xmit()` to perform a confirmed 8-byte write through freed Tx-ring storage, with crash plausible but exploit-oriented reuse unproven.
======================================================================
ABOUT THIS REPORT
======================================================================
The original Linux kernel CVE announcement for CVE-2026-98574 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98574
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.
======================================================================
AL-KERNEL CLASSIFICATION RESULT
======================================================================
CVE-2026-98574 MODERATE https://www.kernelcve.org/list/?q=CVE-2026-98574 CHECK WITH IMPACT FROM ORIG NN MODERATE | AEGIS IMPACT MODERATE_KPANIC AEGIS_AS=2 LEGACY=MODERATE_KPANIC RESULT=SAME V39_AEGIS_ONE_STEP_UP=MODERATE->MODERATE_KPANIC (final reconciliation agrees; DECISION: both MODERATE_KPANIC) Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H';*CWE-416;CWE-362;*CWE-664;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:H';BEST CVSS score: '7';DESCR 'A race in the Broadcom GENET shutdown and Wake on LAN suspend paths can leave Tx completion polling active after the transmit queues are disabled. An in flight completion may call netif_tx_wake_queue, allowing bcmgenet_xmit to write through transmit rings after they have been freed. KASAN confirms an 8 byte use after free write, making memory corruption and kernel crash plausible, while controlled arbitrary write or privilege escalation is not established. For the CVSS the PR:L value reflects that reliable triggering normally requires a local user or process able to create transmit activity and initiate or influence suspend or interface reconfiguration. AC:H reflects the required race window and device specific state. The issue is not proven directly network reachable because external traffic alone does not establish control over the required shutdown sequence. Automated impact decision path. The original SimpleNet classifier selected MODERATE_KPANIC. The primary LLM estimated paranoid CVSS 7 and the production ActionableScore returned 3 with recommendation Borderline / manual review recommended. The production rules then evaluated CVSS thresholds and ActionableScore thresholds. Recorded rule transitions were ActionableScore thresholds stage MODERATE_KPANIC to MODERATE because the ActionableScore threshold rule was applied. final reconciliation stage MODERATE to MODERATE_KPANIC because the cross model evidence reconciliation rule was applied. The legacy KP specialist has no review artifact for this run. The legacy FD or DH downgrade specialist has no review artifact for this run. Exact triggered rule markers were DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN4 and V39_AEGIS_ONE_STEP_UP and MANUAL_REVIEW_REQUIRED. The independent weaker Aegis shadow evaluated CVSS 3.1 and ActionableScore 2 with primitive class CLASS_B and manual review REQUIRED. Its independently reconciled impact was MODERATE_KPANIC. Cross model aggregation changed the production result under an enabled evidence gated merge rule. The final reported impact is MODERATE_KPANIC.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline / manual review recommended (with actual score 3) MAYBE REMOTE DANGER UAF NETWORK DMAorINTERRUPT HARDWARE LINUS QDISC DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN4 KPANIC V39_AEGIS_ONE_STEP_UP MANUAL_REVIEW_REQUIRED - - checked
======================================================================
ACTIONABLESCORE ANALYSIS
======================================================================
ActionableScore=3
PrimitiveClass=CLASS_B
RealUAF=YES
HostAdminRequired=UNKNOWN
NamespaceScopedPrivilege=UNKNOWN
ImportantCandidate=NO
ManualReview=RECOMMENDED
AutoDowngradeAllowed=YES
RequiresHostUID0=UNKNOWN
AuthorizationDecisionBypass=NO
ProtectedResourceImpact=NONE
B4PendingReview=NO
B4PendingConfirmed=NO
1. ActionableScore
* Raw base score: 3.
* Conservative score: 3; no floor or cap applied.
* Raw paranoid score: 3.
* Paranoid score: 3; no technically supported extra exploit-leverage point.
* Final recommended bucket: **Borderline / manual review recommended**::
2. Signal breakdown
* +2 — Real UAF/lifetime violation: Tx rings are freed while a completion can wake the stopped queue, after which `bcmgenet_xmit()` writes through the stale ring.
* +1 — Plausible kernel crash/strong DoS: KASAN confirms an 8-byte post-free write in the transmit path.
* No race penalty: an in-flight completion is required, but the evidence does not establish a genuinely narrow or unreliable race.
* No privilege penalty: the complete trigger’s privilege requirements are unresolved.
* No separate overwrite or structured-leverage bonus: the post-free write is part of the scored UAF, and controlled reclaim, target selection, replacement contents, callbacks, or a later consumer of corrupted state are not shown.
* No extra availability or C/I points: these would duplicate the crash or rely on theoretical reuse.
* B5-R is not established: there is no retry-accumulated index/offset or demonstrated later consumption of retry-corrupted structured state.
* No authorization bypass exists; B4-PENDING is inapplicable.
3. Reachability analysis
Transmit activity can reach the stale-ring write during interface shutdown or Wake-on-LAN suspend. The reproducer used an MTU change and suspend-related ordering, but the evidence does not establish whether an ordinary user, delegated service, or host administrator can perform the complete sequence. No namespace-scoped capability chain is shown. Broadcom GENET hardware is required, but the supplied evidence does not justify a rare-hardware penalty.
4. Primitive and severity reading
The primitive is a confirmed software write through a freed Tx-ring pointer. It is best treated as fixed stale ring storage rather than an attacker-shaped active structured replacement. The shown effect is an 8-byte heap UAF write and plausible crash; useful post-reallocation corruption is possible but unproven. There is no repeated release/refcount operation, arbitrary write, controlled reclaim, or demonstrated security-boundary crossing. Therefore this is constrained CLASS_B, not CLASS_A, and does not presently require Important preservation.
5. One-sentence report phrase
A suspend/shutdown ordering race permits `bcmgenet_xmit()` to perform a confirmed 8-byte write through freed Tx-ring storage, with crash plausible but exploit-oriented reuse unproven.
6. Manual review advice
MANUAL CHECK RECOMMENDED
Confirm trigger privileges, allocator reuse behavior, descriptor write contents, and whether repeated packet transmission can materially shape post-free corruption.
7. Call-site confidence
Call-site confidence: high
======================================================================
UPSTREAM PATCH SUMMARY
======================================================================
Patch: net: bcmgenet: stop Tx NAPI before disabling the queues [ Upstream
Commit: 63bcc2fee6419963e45e7c2cd698fa862409601d
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=63bcc2fee6419963e45e7c2cd698fa862409601d
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=63bcc2fee6419963e45e7c2cd698fa862409601d
======================================================================
DETAILED REPORT METHODOLOGY
======================================================================
The original Linux kernel CVE announcement for CVE-2026-98574 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98574
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:L/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:H
The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
The Best / paranoid CVSS score: 7
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: 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 [email protected] (and both
send reply to CVE record itself too and see "reply" button below for howto reply).
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