[CVE-2026-64329][MODERATE 7.0] usb: typec: ucsi: ccg: Fix use-after-free of ucsi on remove [ Upstream

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

CVE: CVE-2026-64329
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: usb: typec: ucsi: ccg: Fix use-after-free of ucsi on remove [ Upstream
Commit: f1adeb1ff8bef1467d6961059810795d02bbad5d
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=f1adeb1ff8bef1467d6961059810795d02bbad5d
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64329
Analysis date: Sat, 25 Jul 2026 08:15:28 -0400
ActionableScore: 5
ActionableScore lower bound: 3
Actionable bucket: Actionable Moderate at minimum
Manual review required: YES

Summary:
A race in the USB Type-C UCSI CCG remove path can free the ucsi object before an in-flight threaded IRQ handler finishes using it, creating a local device-management use-after-free that can crash the kernel and has weak privilege-escalation concern.

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ABOUT THIS REPORT
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The original Linux kernel CVE announcement for CVE-2026-64329 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64329

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-2026-64329	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-667;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '7';DESCR 'A use-after-free can occur in the USB Type-C UCSI CCG remove path because ucsi_destroy can free the ucsi object before free_irq waits for a threaded IRQ handler that may already be running. The in flight ccg_irq_handler can call ucsi_notify_common with the freed ucsi pointer and may schedule connector change handling, creating a race between device removal and interrupt processing. For the CVSS the PR:L is used for the paranoid score because reliable triggering normally requires local ability to influence driver removal, device unbind, module unload, or a privileged service path rather than remote packet access. The issue is not network reachable. Impact is at least local denial of service via kernel crash and in worst case may allow privilege escalation due to use-after-free memory corruption, so manual review is recommended.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 4)	YES	USB ERRORPATH UAF HARDWARE  DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5	NO	NO	checked

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ACTIONABLESCORE ANALYSIS
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## 1. ActionableScore

ActionableScore=5
ActionableScoreLower=3

Conservative score: 3
Paranoid score: 5

Final recommended bucket: **Actionable Moderate at minimum**::

## 2. Signal breakdown

Conservative signals:

* Race-dependent UAF weak primitive: +1. `ucsi_destroy()` can free `uc->ucsi` while a threaded IRQ handler is still able to pass the stale pointer to `ucsi_notify_common()`.
* Real lifetime corruption: +1. This is a real object lifetime ordering bug between `ucsi_destroy()` and `free_irq()`.
* Reliable kernel crash / strong DoS concern: +1. A stale kernel object used from an IRQ thread can plausibly produce an Oops, KASAN UAF, or crash.
* Hard race / timing window: -1. The issue requires overlap between device removal and an in-flight threaded IRQ.
* Requires privileged device removal in typical deployments: -1 applied conservatively as a reduced penalty. Full `-2` is plausible for normal host-root-only unbind/remove paths, but device-management service paths or physical/firmware events can weaken that assumption.

Paranoid additional signals:

* Firmware-mediated or device-event influence: +1. The IRQ side can be influenced by the Type-C controller or connector-change events, although this is not a network trigger.
* Weak LPE concern: +1. The freed `ucsi` pointer is passed into common UCSI logic and may cause stale object reuse beyond a simple immediate NULL/invalid dereference, but no controlled reclaim or overwrite primitive is shown.
* Privileged device-management lifetime corruption path: +1. The corruption occurs in a trusted USB Type-C driver remove/IRQ lifetime path.
* Race-UAF cap applied. This stays capped at 5 because the patch does not show attacker-controlled reclaim, arbitrary write, type confusion, or controlled callback hijack.

Call-site confidence: medium. The patch and commit describe the relevant remove and IRQ call path, but the full downstream behavior of `ucsi_notify_common()` and connector work is not present in the input.

## 3. Reachability analysis

The realistic trigger is local and tied to device removal, driver unbind, module unload, hot-unplug style teardown, or a privileged device-management path. In typical deployments this requires root or administrative control over the device, so ordinary unprivileged users usually cannot trigger it directly.

The IRQ side may be influenced by hardware or firmware events from the USB Type-C controller, but this is not remotely network reachable. Namespaces usually do not reduce the privilege requirement unless a container or service has delegated access to device management, sysfs unbind, module control, or equivalent host device operations.

The affected path is not a broad default user API. It is device and driver specific, but USB Type-C UCSI is common enough that the bug should not be dismissed as purely theoretical.

## 4. Severity interpretation

This behaves stronger than an ordinary Moderate correctness fix because it is an explicit race-based use-after-free in kernel driver code. Realistic exploitation is most likely DoS through a kernel crash during device removal.

Theoretical privilege escalation is possible in the broad UAF sense, but the patch does not show controlled reclaim, attacker-selected replacement object, write-after-free, type confusion, or function-pointer control. Therefore it is not a Strong Important candidate by default, but it is an Actionable Moderate at minimum and should not be auto-closed without manual review.

## 5. One-sentence report phrase

A race in the USB Type-C UCSI CCG remove path can free the ucsi object before an in-flight threaded IRQ handler finishes using it, creating a local device-management use-after-free that can crash the kernel and has weak privilege-escalation concern.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED

Reason: explicit race-based UAF in a kernel IRQ/remove lifetime path. Even though practical triggering likely requires privileged local device-management access and no controlled exploit primitive is shown, the object lifetime class is risky enough for manual triage.

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

Patch: usb: typec: ucsi: ccg: Fix use-after-free of ucsi on remove [ Upstream
Commit: f1adeb1ff8bef1467d6961059810795d02bbad5d
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=f1adeb1ff8bef1467d6961059810795d02bbad5d

Changed files:
  drivers/usb/typec/ucsi/ucsi_ccg.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=f1adeb1ff8bef1467d6961059810795d02bbad5d

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

The original Linux kernel CVE announcement for CVE-2026-64329 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64329

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:H/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: 3
  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: NO
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).