[CVE-2026-64342][MODERATE 7.0] USB: iowarrior: fix use-after-free on disconnect

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

CVE: CVE-2026-64342
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: USB: iowarrior: fix use-after-free on disconnect
Commit: d058d377291567b72aea33b017215cbfb383b0ad
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=d058d377291567b72aea33b017215cbfb383b0ad
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64342
Analysis date: Sat, 25 Jul 2026 13:37:24 -0400
ActionableScore: 5
ActionableScore lower bound: 4
Actionable bucket: Strong Important candidate / Actionable Moderate at minimum
Manual review required: YES

Summary:
A local use after free in the USB iowarrior disconnect path can occur when submitted write URBs survive close and later complete after device teardown, causing at least a kernel crash and requiring manual review for possible UAF exploitation beyond DoS.

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ABOUT THIS REPORT
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The original Linux kernel CVE announcement for CVE-2026-64342 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64342

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
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CVE-2026-64342	MODERATE	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:H/I:H/A:H';*CWE-416;CWE-362;*CWE-664;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '7';DESCR 'A use after free can occur in the USB iowarrior driver because submitted write URBs are not stopped on close and were only killed on disconnect when the device was still marked opened. If a write URB remains pending and the device is disconnected or unbound after the file is closed, the completion handler may run after device teardown and access freed driver state. For the CVSS the PR:L is used for the paranoid score because reliable triggering generally requires a local process that can open or write to the iowarrior device or otherwise coordinate the USB device state. The issue is not network reachable and requires local USB device interaction or an equivalent local test environment. Impact is at least a local denial of service via kernel crash and in worst case may allow confidentiality or integrity impact due to UAF based memory corruption and should be reviewed manually.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Strong Important candidate / Actionable Moderate at minimum (with actual score 5)	YES	DANGER USB UAF HARDWARE LINUS SYZBOT KPANIC 	NO	YES	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=5
ActionableScoreLower=4

## 1. ActionableScore

* Conservative score: 4
* Paranoid score: 5
* Final recommended bucket: **Strong Important candidate / Actionable Moderate at minimum**::

## 2. Signal breakdown

Conservative signals:

* Local unprivileged trigger: +1. A local process with access to the iowarrior device node can issue writes and close the file descriptor.
* Firmware or device mediated external influence: +1. URB completion and disconnect timing are influenced by USB device behavior or by an emulated USB test environment.
* Memory corruption, strong corruption primitive: +2. The commit explicitly describes a use after free in the completion handler.
* Real lifetime corruption: +1. Pending write URBs can outlive close and device teardown.
* Reliable kernel crash / strong DoS: +1. A completion handler using freed state can crash the kernel.
* Hard or unreliable race / special timing required: -1. Triggering requires a pending write URB plus disconnect or unbind timing.
* Rare and difficult to reach subsystem/configuration: -1. The affected driver is device specific and requires iowarrior hardware, emulation, or a matching USB setup.

Paranoid additional signal:

* Weak LPE concern: +1. The UAF occurs in an asynchronous completion-handler path, so limited heap reuse or stale object access risk is technically plausible, but no controlled reclaim or write primitive is demonstrated.

## 3. Reachability analysis

The bug is local, not network reachable. A realistic trigger requires access to an iowarrior character device and a disconnect or unbind event while a submitted write URB is still pending. In normal deployments this is uncommon because the driver is hardware specific, but local desktop, lab, fuzzing, USB gadget, or malicious USB-device scenarios make the path reachable. Namespaces do not substantially help unless the device node is delegated into a container. Full root is not inherently required if local device permissions allow user access.

Call-site confidence: high. The patch is in the disconnect path and the commit directly states that submitted write URBs must be killed to avoid UAF in the completion handler.

## 4. Severity interpretation

This is more than an ordinary Moderate because it is a real kernel lifetime bug and not just a warning or resource leak. The conservative interpretation is local DoS with UAF-backed memory corruption but no proven confidentiality or integrity primitive. The paranoid interpretation is Actionable Moderate because asynchronous callback UAF bugs can sometimes become exploitable after heap shaping, but the patch does not demonstrate a reliable LPE chain.

## 5. One-sentence report phrase

A local use after free in the USB iowarrior disconnect path can occur when submitted write URBs survive close and later complete after device teardown, causing at least a kernel crash and requiring manual review for possible UAF exploitation beyond DoS.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED

Reason: explicit UAF, asynchronous completion handler, syzbot report, and possible but unproven impact beyond crash.

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UPSTREAM PATCH SUMMARY
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Patch: USB: iowarrior: fix use-after-free on disconnect
Commit: d058d377291567b72aea33b017215cbfb383b0ad
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=d058d377291567b72aea33b017215cbfb383b0ad

Commit description:

Submitted write URBs are not stopped on close() and therefore need to be
stopped unconditionally on disconnect() to avoid use-after-free in the
completion handler.

Fixes: b5f8d46 ("USB: iowarrior: fix use-after-free after driver unbind")
Fixes: 946b960 ("USB: add driver for iowarrior devices.")
Reported-by: syzbot+ad2aac2febc3bedf0962@syzkaller.appspotmail.com
Link: https://lore.kernel.org/all/6a0ce39b.170a0220.39a13.0007.GAE@google.com/
Cc: stable <stable@kernel.org>
Signed-off-by: Johan Hovold <johan@kernel.org>
Link: https://patch.msgid.link/20260523170523.1074563-1-johan@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  drivers/usb/misc/iowarrior.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=d058d377291567b72aea33b017215cbfb383b0ad

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

The original Linux kernel CVE announcement for CVE-2026-64342 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64342

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:N/I:N/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: 4
  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).