[CVE-2026-98025][MODERATE 7.0] net: usb: cx82310_eth: drop URB after 0xffff reboot sentinel to prevent partial_data heap overflow [ Upstream

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

CVE: CVE-2026-98025
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: net: usb: cx82310_eth: drop URB after 0xffff reboot sentinel to prevent partial_data heap overflow [ Upstream
Commit: 3bd689409bb1c93bdc6dd8ec6cbf5161bc4f0287
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=3bd689409bb1c93bdc6dd8ec6cbf5161bc4f0287
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98025
Analysis date: Sat, 26 Sep 2026 15:31:05 -0400
ActionableScore: 5
ActionableScore lower bound: unknown
Actionable bucket: Actionable Moderate / Strong Important candidate requiring manual review
Manual review required: YES

Summary:
No one-sentence report phrase was found.

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

The original Linux kernel CVE announcement for CVE-2026-98025 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98025

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
======================================================================

CVE-2026-98025	MODERATE	https://www.kernelcve.org/list/?q=CVE-2026-98025 CHECK WITH IMPACT FROM ORIG NN LOW	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:P/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H';CWE-122;*CWE-787;CWE-125;*CWE-20;Other CVSS 'AV:P/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:H';BEST CVSS score: '6.8';DESCR 'A heap based buffer overflow in the cx82310_eth USB Ethernet driver occurs because a 0xffff router reboot sentinel schedules reenable work but then falls through into incomplete packet handling. A controlled CX82310 device can send a 4096 byte USB receive buffer beginning with ff ff, causing up to 4094 bytes to be copied into a partial_data buffer allocated for only 1516 bytes. Later processing also reads beyond the partial buffer and the next receive buffer while constructing a malformed large frame. For the CVSS the PR:N metric is used because an attacker only needs control of the connected USB networking device and does not need a local account or code execution on the host. The attack vector is physical AV:P and the issue is not directly network reachable. Impact is at least denial of service through kernel memory corruption and may include confidentiality integrity impact or privilege escalation if the controlled heap overflow can be developed into a reliable kernel exploitation primitive. In practice exploitation requires physical access to attach a malicious device or prior compromise of an already attached USB router or network adapter.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate / Strong Important candidate requiring manual review (with actual score 5)	YES	USB NETWORK HARDWARE LINUS BOOT KPANIC PACKET  KPANIC INCREASED_TO_HIGH_BASED_ON_GUESSCVSS DECREASED_TO_MODERATE7_BASED_ON_FALSEPOSCHECKOFDH	NO	NO	checked

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

ActionableScore=5
PrimitiveClass=CLASS_A
RealUAF=NO
HostAdminRequired=NO
NamespaceScopedPrivilege=UNKNOWN
ImportantCandidate=YES
ManualReview=REQUIRED
AutoDowngradeAllowed=NO

1. ActionableScore

* Raw conservative score: 2
* Conservative score: 5
* Raw paranoid score: 2
* Paranoid score: 5
* Applied conservative floor: 2 -> 5 because a concrete attacker-controlled kernel heap overwrite is established.
* Applied paranoid floor: 2 -> 5 because a concrete attacker-controlled kernel heap overwrite is established.
* Final recommended bucket: **Actionable Moderate / Strong Important candidate requiring manual review**::

2. Signal breakdown

* +2 Strong corruption primitive. The affected USB device controls up to 4094 copied bytes after supplying the 0xffff sentinel. The destination partial_data allocation is 1516 bytes, producing a concrete heap out of bounds write of up to approximately 2578 bytes.
* +1 Firmware-mediated external influence. The vulnerable receive path consumes data delivered by an attached CX82310 USB networking device. This is not direct network reachability because device mediation is required.
* +1 Reliable kernel crash or strong DoS. A large heap overwrite followed by out of bounds reads during subsequent URB handling can realistically crash or corrupt the host kernel.
* -2 Physical-only or rare hardware requirement. Triggering requires a CX82310 USB Ethernet device or router to be physically attached to the target, or an already attached compatible device to be compromised and attacker controlled.

No double-counting:

* No additional integrity point was awarded. The overwrite is concrete, but unauthorized modification of a specific protected kernel object, credential, policy object, or file-backed data is not demonstrated.
* No confidentiality point was awarded. Subsequent out of bounds reads are established, but no path returning leaked data to userspace, network peers, or the device is demonstrated.
* No separate availability point was awarded. The kernel crash risk is already counted as the reliable DoS signal.
* No direct remote reachability point was awarded. The vulnerable data enters from USB device firmware or hardware, not directly from an IP network peer.
* No controlled reclaim, object replacement, arbitrary write, callback control, or demonstrated LPE was established.
* No generic subsystem rarity penalty was used. The negative signal is based on the concrete requirement for a specific attached USB hardware path, not merely on the fact that this is a driver.

3. Reachability analysis

The attacker model is a malicious or compromised CX82310 USB Ethernet adapter or router connected to the host. The device sends a receive URB beginning with the 0xffff reboot marker and sufficient trailing attacker-controlled bytes.

No local user account, host root privilege, CAP_NET_ADMIN, or host-admin-equivalent permission is required for the device to transmit receive data after the driver is active. Therefore HostAdminRequired is NO.

The complete trigger is not namespace-scoped. Network namespaces do not control USB device attachment, USB URB delivery, or the driver receive path. NamespaceScopedPrivilege is UNKNOWN because namespace capabilities are not relevant to the demonstrated hardware trigger.

A prior condition exists: the target must use the affected cx82310_eth driver with a compatible USB networking device attached. This is a material hardware and physical-access limitation. A remote attacker could only reach this path after compromising firmware or control of an already attached device, which is not established by the supplied patch.

The issue is not a timing race. The trigger is an ordered packet-format condition and is repeatable whenever the affected device can provide the crafted URB sequence.

4. Primitive and severity interpretation

The exact primitive is a device-controlled heap based out of bounds write followed by device-influenced out of bounds reads. The 0xffff reboot sentinel bypasses the normal CX82310_MTU bound because the oversized-length validation is in the else branch of the sentinel comparison.

The write is not merely a stale pointer or crash-only invalid dereference. The attacker-controlled USB device can supply a payload of up to 4094 bytes that is copied into a 1516 byte kmalloc allocation. The overwrite target is constrained to heap memory adjacent to partial_data and no target-address selection, controlled reclaim, function pointer overwrite, arbitrary read or write, or credential manipulation is demonstrated.

This is not a UAF and there is no repeated release or refcount mutation. RealUAF is NO.

PrimitiveClass is CLASS_A because an attacker-influenced heap overwrite is directly established. The primitive remains materially constrained by the USB hardware requirement and by the absence of demonstrated control over the adjacent heap object. Nevertheless, automatic downgrade is unsafe because the patch establishes actual kernel memory corruption rather than a warning, a bookkeeping mismatch, or a pure device-local failure.

The demonstrated practical consequence is kernel corruption and likely kernel crash or DoS. Privilege escalation, confidentiality impact, and integrity impact remain plausible consequences of successful exploitation of the heap overwrite, but they are not established by the supplied patch and are not separately scored.

ImportantCandidate is YES because the bug is a concrete controlled kernel heap corruption primitive. AutoDowngradeAllowed is NO because closing it as an ordinary driver crash would discard unresolved exploitation potential from a large device-controlled heap overwrite.

Likely operational severity is Actionable Moderate at minimum. It should receive manual exploitability review, especially for systems that commonly attach the affected router or USB Ethernet hardware in trusted physical environments.

5. One-sentence report phrase

A malicious attached CX82310 USB networking device can exploit a reboot sentinel parsing flaw to overflow a 1516 byte kernel heap buffer with up to 4094 attacker-controlled bytes, causing kernel corruption and likely denial of service.

6. Manual review recommendation

MANUAL CHECK REQUIRED

A concrete attacker-controlled heap overflow is established, while practical control of adjacent heap objects and non-DoS exploitation consequences remain unresolved.

7. Call-site confidence

Call-site confidence: medium

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

Patch: net: usb: cx82310_eth: drop URB after 0xffff reboot sentinel to prevent partial_data heap overflow [ Upstream
Commit: 3bd689409bb1c93bdc6dd8ec6cbf5161bc4f0287
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=3bd689409bb1c93bdc6dd8ec6cbf5161bc4f0287

Changed files:
  drivers/net/usb/cx82310_eth.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=3bd689409bb1c93bdc6dd8ec6cbf5161bc4f0287

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

The original Linux kernel CVE announcement for CVE-2026-98025 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98025

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:P/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:H
  The Best / paranoid CVSS vector: AV:P/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
  The Best / paranoid CVSS score: 6.8

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: 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).