[CVE-2026-72483][MODERATE REGULAR] usb: host: max3421: Fix shift-out-of-bounds in max3421_hub_control() [ Upstream commit cff06b03b530ae1fe8a13e93a7848f2130e00fb4 ]

[CVE-2026-72483][MODERATE REGULAR] usb: host: max3421: Fix shift-out-of-bounds in max3421_hub_control() [ Upstream commit cff06b03b530ae1fe8a13e93a7848f2130e00fb4 ]

[AL-KERNEL]

CVE: CVE-2026-72483
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: usb: host: max3421: Fix shift-out-of-bounds in max3421_hub_control() [ Upstream commit cff06b03b530ae1fe8a13e93a7848f2130e00fb4 ]
Commit: e5fa9d8f40746ec3447335c9642c03410f5fd3af
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=e5fa9d8f40746ec3447335c9642c03410f5fd3af
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72483
Analysis date: Sat, 15 Aug 2026 21:04:31 -0400
ActionableScore: 4
ActionableScore lower bound: 3
Actionable bucket: Borderline, manual review recommended. Not an Important candidate based on supplied evidence
Manual review required: YES

Summary:
A local task with access to the MAX3421 root hub device can send a malformed USBDEVFS_CONTROL request with wValue 32 or larger, triggering shift-out-of-bounds undefined behavior and corruption of USB hub port_status state, with realistic impact limited to local denial of service or device state confusion.

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

The original Linux kernel CVE announcement for CVE-2026-72483 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72483

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: YES

A detailed explanation of the methodology and priority rules is included
at the end of this message.

======================================================================
AL-KERNEL CLASSIFICATION RESULT
======================================================================

CVE-2026-72483	MODERATE	CHECK WITH IMPACT FROM ORIG NN IMPORTANT	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H';CWE-1335;*CWE-20;CWE-682;Other CVSS 'AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '5.5';DESCR 'A shift out of bounds bug in max3421_hub_control can be triggered when a local task sends a USBDEVFS_CONTROL ioctl to the MAX3421 root hub with wValue 32 or larger. The unchecked value is used as the shift count while updating port_status, which invokes undefined behavior and can corrupt virtual hub port state bits. For the CVSS the PR:L is used in the paranoid score because the attacker needs local code execution and access to the root hub device node, but full root privileges may not be required if USB device access is delegated. The issue is not network reachable. Impact is mainly denial of service or local USB hub state corruption. No concrete UAF, OOB write, or privilege escalation primitive is shown by the patch context.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline, manual review recommended. Not an Important candidate based on supplied evidence (with actual score 4)  SKIP CVE-2026-72483 UNKNOWN SKIP No affected files built, so skip this CVE NO  - - unknown 	MAYBE	WRITE OOB DANGER USB IMPROVEONLY LINUS  DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS_AND_CIANNH	-	-	checked

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

ActionableScore=4
ActionableScoreLower=3

## 1. ActionableScore

* Conservative score: 3
* Paranoid score: 4
* Final recommended bucket: **Borderline, manual review recommended. Not an Important candidate based on supplied evidence**

## 2. Signal breakdown

Triggered signals:

* Local unprivileged or low-privileged trigger: +1
  A local userspace task with access to the MAX3421 root hub device node via `/dev/bus/usb/.../001` can issue `USBDEVFS_CONTROL` with `wValue >= 32`.

* Memory corruption, weak or indirect corruption candidate: +1
  The bug is a shift-out-of-bounds undefined behavior that corrupts `port_status` bits. This is kernel state corruption, but not a demonstrated OOB write, UAF, arbitrary write, type confusion, or reclaim primitive.

* Reliable device-path DoS concern: +1
  Corrupting root hub port state can confuse hub status handling and plausibly disrupt the USB host path. The patch does not show a guaranteed kernel panic, so this is weaker than a strong memory-corruption DoS.

Paranoid-only signal:

* Privileged kernel/device-management state corruption path: +1
  The corrupted object is in a USB host controller driver and affects trusted hub/device-management state. This justifies manual review, but not Important severity by itself.

Not applied:

* Remote reachable: +0
  No network trigger.

* Firmware-mediated external influence: +0
  The triggering input is userspace ioctl data, not firmware-controlled data.

* Strong memory corruption primitive: +0
  No UAF, double-free, OOB write, heap overwrite, arbitrary write, or page-cache corruption is shown.

* Privilege escalation plausible: +0
  No supported LPE primitive is visible from the patch.

* Confidentiality impact plausible: +0
  No readback or information disclosure path is shown.

* Integrity impact plausible: +0 for system security integrity
  There is local hub state corruption, but no demonstrated corruption of protected files, credentials, memory ownership, or security policy state.

* Rare hardware/config penalty: not applied
  MAX3421 is not a broad default path, but on affected systems the interface is reachable through ordinary local USB device access. I would not subtract unless triaging only generic server exposure.

## 3. Reachability analysis

The bug is locally reachable by a process that can open the affected USB root hub device node and issue `USBDEVFS_CONTROL`. In typical deployments this may require root, a USB management group, udev-granted device access, or a container/device passthrough configuration. It is not remotely reachable and does not sit on a common network packet-processing path. Namespaces or containers matter only if the USB device node is delegated into the environment.

The affected path is hardware and driver dependent. It requires a system using the MAX3421 USB host controller driver, so exposure is narrower than core USB or common xHCI paths. Realistic exploitation appears to be local device disruption or state confusion, not demonstrated privilege escalation.

## 4. Severity interpretation

This behaves like a borderline Moderate issue rather than an Important-class kernel vulnerability. The theoretical concern is kernel undefined behavior and corruption of driver-maintained hub state. The realistic evidence supports local denial of service or USB host state confusion.

There is no demonstrated arbitrary memory corruption, no UAF, no attacker-controlled object replacement, no callback control, no file-backed or page-cache corruption, and no security-boundary bypass. Manual review is still reasonable because attacker-controlled undefined behavior in kernel driver state can sometimes have deeper consequences than the small patch shows.

## 5. One-sentence report phrase

A local task with access to the MAX3421 root hub device can send a malformed USBDEVFS_CONTROL request with wValue 32 or larger, triggering shift-out-of-bounds undefined behavior and corruption of USB hub port_status state, with realistic impact limited to local denial of service or device state confusion.

## 6. Manual review recommendation

MANUAL CHECK RECOMMENDED

Reason: the issue is not strong enough for Important based on the patch alone, but attacker-controlled undefined behavior in a kernel USB host driver and corruption of internal hub state should not be auto-closed without confirming whether the corrupted `port_status` bits can drive any stronger downstream failure path.

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

Patch: usb: host: max3421: Fix shift-out-of-bounds in max3421_hub_control() [ Upstream commit cff06b03b530ae1fe8a13e93a7848f2130e00fb4 ]
Commit: e5fa9d8f40746ec3447335c9642c03410f5fd3af
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=e5fa9d8f40746ec3447335c9642c03410f5fd3af

Commit description:

The `max3421_hub_control()` function handles USB hub class requests
to the virtual root hub. In the `default` branches of both the
`ClearPortFeature` and `SetPortFeature` switch statements, it modifies
`max3421_hcd->port_status` by left shifting 1 by the request's `value`
parameter. However, it does not validate whether this shift will exceed
the width of `port_status`.

So if a malicious userspace task with access to the root hub via
/dev/bus/usb/.../001 issues a USBDEVFS_CONTROL ioctl with `wValue`
greater than or equal to 32, the left shift operation invokes
shift-out-of-bounds undefined behavior. This results in arbitrary
bit corruption of `port_status`, including the normally-immutable
change bits, which can bypass internal state checks and confuse the
hub status.

Fix this by rejecting requests whose `value` exceeds the shift width
before performing the shift.

This issue was found using a KLEE-based symbolic execution tool for
kernel drivers that I'm currently developing.

Fixes: 2d53139f3162 ("Add support for using a MAX3421E chip as a host driver.")
Signed-off-by: Seungjin Bae <eeodqql09@gmail.com>
Link: https://patch.msgid.link/20260518224901.1887013-1-eeodqql09@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Diffstat -rw-r--r-- drivers/usb/host/max3421-hcd.c 4

Changed files:
  drivers/usb/host/max3421-hcd.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=e5fa9d8f40746ec3447335c9642c03410f5fd3af

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

The original Linux kernel CVE announcement for CVE-2026-72483 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72483

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:L/PR:L/UI:N/S:U/C:N/I:N/A:L
  The Best / paranoid CVSS vector: AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS score: 5.5

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: 4

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).