[CVE-2026-64334][LOW] USB: serial: digi_acceleport: fix hard lockup on disconnect

[CVE-2026-64334][LOW] USB: serial: digi_acceleport: fix hard lockup on disconnect

[AL-KERNEL]

CVE: CVE-2026-64334
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: USB: serial: digi_acceleport: fix hard lockup on disconnect
Commit: 6e51147c2744d15730084dc89cc99180d3de4184
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=6e51147c2744d15730084dc89cc99180d3de4184
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64334
Analysis date: Sat, 25 Jul 2026 07:23:34 -0400
ActionableScore: 2
ActionableScore lower bound: 1
Actionable bucket: Ordinary Moderate / Low-like
Manual review required: NO

Summary:
A persistent OOB write URB submission failure in the `digi_acceleport` USB serial driver can cause an infinite loop with interrupts disabled during a disconnect race, leading to a local or physical denial of service via hard lockup.

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

The original Linux kernel CVE announcement for CVE-2026-64334 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64334

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

CVE-2026-64334	LOW	CHECK WITH IMPACT FROM ORIG NN MODERATE	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H';*CWE-835;**CWE-400;CWE-755;Other CVSS 'AV:P/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '4.7';DESCR 'digi_acceleport can enter an infinite loop with interrupts disabled when OOB write URB submission fails persistently during a disconnect race. A local user with access to the USB serial port may trigger the vulnerable path by racing open(), set_termios(), or close() with device removal or another condition that makes usb_submit_urb fail. For the CVSS the PR:L value is used for the paranoid score because reliable triggering can require only a local user context with access to the tty or USB serial device rather than full administrator privileges. The issue is not network reachable and requires local or physical interaction with the affected USB serial device. Impact is denial of service via hard lockup only. There is no evidence of UAF, OOB access, information disclosure, or privilege escalation from this patch context.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like (with actual score 2)	YES	WRITE OOB DEADLOCK USB PRINTF-TTY SIMPLEFIX RACE 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
======================================================================

ActionableScore=2
ActionableScoreLower=1

## 1. ActionableScore

* Conservative score: 1
* Paranoid score: 2
* Final recommended bucket: **Ordinary Moderate / Low-like**

## 2. Signal breakdown

Triggered positive signals:

* Reliable kernel crash / strong DoS: +1
  Persistent `usb_submit_urb()` failure can keep the loop running with interrupts disabled, causing a hard lockup.

* Availability impact realistic: +1 in paranoid scoring
  The impact can be host-visible hard lockup rather than a minor local failure. This is counted only in the paranoid score to avoid double-counting ordinary crash impact.

* Local unprivileged trigger: +1 in paranoid scoring
  A local user with access to the affected USB serial tty may be able to race `open()`, `set_termios()`, or `close()` with disconnect or another URB submission failure condition.

Negative signals:

* Hard or unreliable race / special timing required: -1
  The issue depends on a race with disconnect or persistent URB submission failure.

* Physical-only or rare hardware-only condition: -2 conservative, partially relaxed in paranoid scoring
  The clearest trigger involves a specific USB serial device and disconnect behavior.

* Rare AND difficult-to-reach subsystem/configuration: -1
  `digi_acceleport` is a legacy USB serial driver and not a broad/default kernel attack surface.

No triggered signals:

* No generic memory corruption.
* No UAF, OOB write, double free, type confusion, refcount abuse, or page-cache/shared-page corruption.
* No plausible privilege escalation primitive.
* No network reachability.

## 3. Reachability analysis

The realistic trigger requires the affected Digi AccelePort USB serial driver, an attached or disconnecting compatible USB serial device, and an operation that sends OOB commands while `usb_submit_urb()` persistently fails. The most explicit scenario is physical or local interaction with the USB device during `open()`, `set_termios()`, or `close()`.

Namespaces and containers do not meaningfully broaden exposure unless the USB serial device node is delegated into the container. The path is not network reachable and is not a common default remote attack surface.

Call-site confidence: high. The commit message directly names the relevant call situations and the patch shows the loop condition and missing error break.

## 4. Severity interpretation

This behaves like an ordinary Moderate / Low-like kernel DoS issue rather than an Important-class vulnerability. The theoretical impact is severe availability loss via hard lockup, but the exploitation conditions are narrow and hardware/local-interaction dependent. There is no evidence of memory corruption, information disclosure, privilege escalation, or a reusable exploit primitive beyond denial of service.

## 5. One-sentence report phrase

A persistent OOB write URB submission failure in the `digi_acceleport` USB serial driver can cause an infinite loop with interrupts disabled during a disconnect race, leading to a local or physical denial of service via hard lockup.

## 6. Manual review recommendation

NO MANUAL CHECK NEEDED

Reason: the bug is DoS-only, hardware-specific, not network reachable, and the patch does not indicate memory corruption or privilege escalation potential.

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

Patch: USB: serial: digi_acceleport: fix hard lockup on disconnect
Commit: 6e51147c2744d15730084dc89cc99180d3de4184
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=6e51147c2744d15730084dc89cc99180d3de4184

Commit description:

If submitting the OOB write urb fails persistently (e.g if the device is
being disconnected) the driver would loop indefinitely with interrupts
disabled.

Check for urb submission errors when sending OOB commands to avoid
hanging if, for example, open(), set_termios() or close() races with a
physical disconnect.

This is issue was flagged by Sashiko when reviewing an unrelated change
to the driver.

Link: https://sashiko.dev/#/patchset/20260610132232.356139-1-johan%40kernel.org?part=1
Fixes: 1da177e ("Linux-2.6.12-rc2")
Cc: stable@vger.kernel.org
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Johan Hovold <johan@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  drivers/usb/serial/digi_acceleport.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=6e51147c2744d15730084dc89cc99180d3de4184

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

The original Linux kernel CVE announcement for CVE-2026-64334 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64334

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:H/PR:L/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS score: 4.7

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: 1
  Paranoid ActionableScore: 2

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).