[CVE-2026-46103][LOW] can: ucan: fix devres lifetime

[CVE-2026-46103][LOW] can: ucan: fix devres lifetime

[AL-KERNEL]

CVE: CVE-2026-46103
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: can: ucan: fix devres lifetime
Commit: 4b7d07747400cfd7eff1ba7b8b5a7c8d5a58f705
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=4b7d07747400cfd7eff1ba7b8b5a7c8d5a58f705
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46103
Analysis date: Wed, 27 May 2026 11:57:47 -0400
ActionableScore: 1
ActionableScore lower bound: 0
Actionable bucket: Ordinary Moderate / Low-like
Manual review required: NO

Summary:
A UCAN USB CAN control buffer was tied to the parent USB device instead of the interface, causing a local resource leak on driver unbind without memory corruption or privilege escalation.

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

The original Linux kernel CVE announcement for CVE-2026-46103 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46103

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: LOW
Manual review required: NO

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-2026-46103	LOW	CHECK	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-772;*CWE-401;CWE-404;Other CVSS 'AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '5.5';DESCR 'A resource leak can occur in the ucan USB CAN driver because the control transfer buffer was allocated with devres tied to the parent USB device instead of the USB interface. Repeated interface unbind and bind cycles without physical disconnect can keep the buffer alive longer than intended and cause resource retention. For the CVSS the PR:L is used only in the paranoid score where a reduced privilege service or delegated container can repeatedly trigger USB interface unbind, bind, or probe deferral. The typical case is closer to PR:H because USB driver unbind and device configuration changes normally require administrative device management privileges. The issue is not network reachable and does not involve UAF, out of bounds access, arbitrary write, information disclosure, or privilege escalation. Impact is denial of service only through resource leakage after repeated operations.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like (with actual score 1)	YES	USB SIMPLEFIX LEAK NETWORK HARDWARE LINUS  DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS_AND_CIANNH DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3	NO	NO	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=1
ActionableScoreLower=0

## 1. ActionableScore

* Conservative score: 0
* Paranoid score: 1
* Final recommended bucket: **Ordinary Moderate / Low-like**::

## 2. Signal breakdown

Conservative signals:

* Availability impact weakly plausible: +1
  Repeated unbind or probe deferral can retain a small control-transfer buffer longer than intended.

* Requires admin/device-management control in typical deployments: -2
  USB driver unbind, rebind, or configuration changes normally require privileged device management.

* Physical/device-specific condition: -1
  Requires a Theobroma UCAN USB CAN device or relevant driver binding.

Paranoid signal:

* Delegated device-management concern: +1
  Some systems may expose USB interface unbind/rebind or probe control to a service account, test harness, or container.

No signals apply for remote reachability, memory corruption, UAF, OOB access, arbitrary write, information disclosure, privilege escalation, or security-boundary bypass.

## 3. Reachability analysis

The issue is local and device-management related. It occurs when the UCAN driver is unbound from a USB interface without the parent USB device being disconnected, because the devres allocation was tied to the wrong device lifetime.

Namespaces and containers matter only if USB interface management is delegated. The issue is not reachable over CAN traffic or the network. Practical triggering usually requires administrator control over USB driver binding or probe behavior.

## 4. Severity interpretation

This is a Low-like resource leak. The patch fixes devres lifetime binding so the buffer is released at interface unbind.

There is no memory corruption, UAF, data leak, or privilege escalation. The realistic impact is minor resource retention after repeated privileged operations.

## 5. One-sentence report phrase

A UCAN USB CAN control buffer was tied to the parent USB device instead of the interface, causing a local resource leak on driver unbind without memory corruption or privilege escalation.

## 6. Manual review recommendation

NO MANUAL CHECK NEEDED

This is a small, device-specific resource leak with privileged or delegated unbind requirements and no supported security impact beyond local resource retention.

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

Patch: can: ucan: fix devres lifetime
Commit: 4b7d07747400cfd7eff1ba7b8b5a7c8d5a58f705
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=4b7d07747400cfd7eff1ba7b8b5a7c8d5a58f705

Commit description:

USB drivers bind to USB interfaces and any device managed resources
should have their lifetime tied to the interface rather than parent USB
device. This avoids issues like memory leaks when drivers are unbound
without their devices being physically disconnected (e.g. on probe
deferral or configuration changes).

Fix the control message buffer lifetime so that it is released on driver
unbind.

Fixes: 9f2d3ea ("can: ucan: add driver for Theobroma Systems UCAN devices")
Cc: stable@vger.kernel.org	# 4.19
Cc: Jakob Unterwurzacher <jakob.unterwurzacher@theobroma-systems.com>
Signed-off-by: Johan Hovold <johan@kernel.org>
Link: https://patch.msgid.link/20260327104520.1310158-1-johan@kernel.org
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  drivers/net/can/usb/ucan.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=4b7d07747400cfd7eff1ba7b8b5a7c8d5a58f705

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

The original Linux kernel CVE announcement for CVE-2026-46103 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46103

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:H/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: 0
  Paranoid ActionableScore: 1

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: LOW
KPANIC detected for this report: NO
Published priority for this report (same as in Subject): LOW

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).