[CVE-2026-68372][MODERATE REGULAR] usb: core: port: Deattach Type-C connector on component unbind

[CVE-2026-68372][MODERATE REGULAR] usb: core: port: Deattach Type-C connector on component unbind

[AL-KERNEL]

CVE: CVE-2026-68372
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: usb: core: port: Deattach Type-C connector on component unbind
Commit: 78d361e60caf1999d51bda0e1b1004f5d39fcfbc
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=78d361e60caf1999d51bda0e1b1004f5d39fcfbc
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68372
Analysis date: Mon, 10 Aug 2026 10:03:12 -0400
ActionableScore: 4
ActionableScore lower bound: 3
Actionable bucket: Borderline manual review recommended / Actionable Moderate not proven
Manual review required: YES

Summary:
A race in USB Type C connector unbind can leave stale Type C device pointers after dock unplug, allowing later UCSI partner cleanup to dereference freed USB device state and cause Type C state corruption or kernel crash.

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

The original Linux kernel CVE announcement for CVE-2026-68372 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68372

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-2026-68372	MODERATE	CHECK WITH IMPACT FROM ORIG NN MODERATE	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:P/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H';CWE-362;*CWE-416;*CWE-672;Other CVSS 'AV:P/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '6.4';DESCR 'USB Type C connector unbind can race with USB disconnect and UCSI partner unregister. connector_unbind clears port_dev connector without first calling typec_deattach, leaving typec port usb2_dev or usb3_dev pointing to a USB device that is being freed. A later typec_unregister_partner path can use the stale device pointer through sysfs_remove_link and dev_name, producing state corruption, warnings, or a use-after-free with a kernel crash. For the CVSS the PR:N is used for the paranoid score because physical hotplug and unplug of an affected Thunderbolt or USB Type C dock does not require OS privileges, although reliable triggering requires physical access to the device and race timing. The issue is not network reachable. Impact is at least local physical denial of service and in worst case may allow confidentiality or integrity impact due to kernel use-after-free, so manual review is recommended.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline manual review recommended / Actionable Moderate not proven (with actual score 4)	YES	USB RACE UAF HARDWARE  DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5	YES	NO	checked

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

ActionableScore=4
ActionableScoreLower=3

## 1. ActionableScore

* Conservative score: 3
* Paranoid score: 4
* Final recommended bucket: **Borderline manual review recommended / Actionable Moderate not proven**::

## 2. Signal breakdown

Conservative signals:

* +1 Local unprivileged-like trigger: physical hotplug or unplug of an affected Thunderbolt or USB Type C dock does not require OS privileges.
* +1 Memory corruption, weak primitive: the patch description explicitly describes a stale pointer and possible UAF, but no attacker-controlled reclaim, write-after-free, callback control, or type confusion is shown.
* +1 Real lifetime corruption: port->usb2_dev or port->usb3_dev can remain pointing to a USB device that is being freed or already freed.
* +1 Reliable kernel crash / strong DoS: the described path causes warnings, corrupted Type C or UCSI state, failed dock re-enumeration, and may become a UAF crash with worse timing.
* +1 Broad/common subsystem: USB core, Type C, UCSI, and Thunderbolt dock hotplug are common on many client and workstation systems.
* -1 Hard or unreliable race: exploitation depends on timing between connector_unbind(), usb_disconnect(), and UCSI partner unregister.
* -2 Physical-only or hardware-specific condition: realistic triggering requires physical access and affected Type C / Thunderbolt dock hardware.

Paranoid additional signal:

* +1 Privileged device-management lifetime corruption path: the stale pointer affects kernel device-management state across USB, Type C, UCSI, sysfs, PCIe recovery, and NIC reset paths.

Race-UAF downgrade applied: no LPE bonus is awarded because there is no demonstrated reclaim, controlled replacement, writable stale access, callback dispatch, refcount takeover, or arbitrary write.

## 3. Reachability analysis

The bug is triggered by physical hotplug or unplug of an affected Thunderbolt or USB Type C dock. It is not network reachable. No local OS account or capability is required if the attacker has physical access to the port and device.

Namespaces and containers do not materially change reachability because the trigger is hardware hotplug rather than a namespaced syscall or netlink API. The affected path is common on systems using USB Type C, UCSI, or Thunderbolt docks, but the practical condition is still hardware dependent and timing dependent.

Call-site confidence: high. The commit message gives the relevant teardown paths and shows the stale pointer flow through typec_unregister_partner(), typec_partner_unlink_device(), sysfs_remove_link(), and dev_name().

## 4. Severity interpretation

This is stronger than an ordinary warning-only Moderate because the patch context explicitly identifies stale device pointers and a possible use-after-free. Realistic impact is mainly physical local denial of service, corrupted dock or Type C state, failed re-enumeration, warnings, and possible kernel crash.

It does not currently justify Important-class scoring by itself. The UAF is race-dependent and no practical privilege escalation primitive is shown. Theoretical memory corruption exists, but realistic exploitation evidence is limited to state corruption and DoS.

## 5. One-sentence report phrase

A race in USB Type C connector unbind can leave stale Type C device pointers after dock unplug, allowing later UCSI partner cleanup to dereference freed USB device state and cause Type C state corruption or kernel crash.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED

Reason: explicit stale pointer and UAF candidate in a common kernel device-management path, even though realistic exploitation appears physical-only, timing-dependent, and mainly DoS.

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

Patch: usb: core: port: Deattach Type-C connector on component unbind
Commit: 78d361e60caf1999d51bda0e1b1004f5d39fcfbc
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=78d361e60caf1999d51bda0e1b1004f5d39fcfbc

Commit description:

connector_unbind() is the mirror of connector_bind(), but it is missing
the symmetric call to typec_deattach() that connector_bind() makes via:

    if (port_dev->child)
        typec_attach(port_dev->connector, &port_dev->child->dev);

When a Thunderbolt dock is unplugged, two teardown paths race:

1. The component framework calls connector_unbind() first, which sets
   port_dev->connector = NULL without calling typec_deattach().  This
   leaves port->usb2_dev/port->usb3_dev in struct typec_port pointing at
   the USB device that is about to be freed.

2. usb_disconnect() then calls typec_deattach(port_dev->connector, ...),
   but port_dev->connector is already NULL, so the call is a no-op and
   port->usb2_dev is never cleared.

3. Concurrently, UCSI detects a PD partner-disconnect event and calls
   typec_unregister_partner(), which reads port->usb2_dev (now a dangling
   pointer to freed memory) and passes it to typec_partner_unlink_device()
   -> sysfs_remove_link() -> dev_name() on the freed device, corrupting
   the typec/UCSI partner state.

This corruption leaves the Thunderbolt tunnel in an inconsistent state on
the next dock hot-plug.  On affected hardware the dock's I225/igc NIC fails
to enumerate: AER fires a slot reset while the igc driver is still
initialising ("PCIe link lost"), and the subsequent igc_reset attempt hits
igc_rd32 on an already-detached device:

    igc 0000:2e:00.0 eth0: PCIe link lost, device now detached
    igc: Failed to read reg 0x0!
    WARNING: CPU: 9 PID: 129 at drivers/net/ethernet/intel/igc/igc_main.c:7005
             igc_rd32+0xa4/0xc0 [igc]
    Call Trace:
     igc_disable_pcie_master+0x16/0xa0 [igc]
     igc_reset_hw_base+0x14/0x170 [igc]
     igc_reset+0x63/0x110 [igc]
     igc_io_slot_reset+0x9e/0xd0 [igc]
     report_slot_reset+0x5d/0xc0
     pcie_do_recovery+0x209/0x400
     aer_isr_one_error_type+0x235/0x430
     aer_isr+0x4e/0x80
     irq_thread+0xf4/0x1f0

4. UCSI later handles the PD partner-disconnect and calls
   typec_unregister_partner(), which still sees the stale port->usb2_dev
   and tries to remove its sysfs link a second time:

   kernfs: can not remove 'typec', no directory
   WARNING: CPU: 6 PID: 55 at fs/kernfs/dir.c:1706 kernfs_remove_by_name_ns+0xe9/0xf0
   Workqueue: events ucsi_handle_connector_change [typec_ucsi]
   Call Trace:
    sysfs_remove_link+0x19/0x50
    typec_unregister_partner+0x6e/0x120 [typec]
    ucsi_unregister_partner+0x107/0x150 [typec_ucsi]
    ucsi_handle_connector_change+0x3ec/0x490 [typec_ucsi]
    process_one_work+0x18e/0x3e0
    worker_thread+0x2e3/0x420
    kthread+0x10a/0x230
    ret_from_fork+0x121/0x140
    ret_from_fork_asm+0x1a/0x30

   With worse timing the same stale pointer is dereferenced after the
   backing memory is freed, turning the warning into a use-after-free.

Fix the asymmetry: call typec_deattach() before clearing
port_dev->connector, matching what connector_bind() does on the bind side.
typec_partner_deattach() is already protected by port->partner_link_lock,
so it serialises safely with the concurrent typec_unregister_partner() path.

Fixes: 1111078 ("usb: Inform the USB Type-C class about enumerated devices")
Cc: stable <stable@kernel.org>
Signed-off-by: Chia-Lin Kao (AceLan) <acelan.kao@canonical.com>
Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Link: https://patch.msgid.link/20260611071201.1235545-1-acelan.kao@canonical.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  drivers/net/ethernet/intel/igc/igc_main.c
  fs/kernfs/dir.c
  drivers/usb/core/port.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=78d361e60caf1999d51bda0e1b1004f5d39fcfbc

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

The original Linux kernel CVE announcement for CVE-2026-68372 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68372

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:N/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS vector: AV:P/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
  The Best / paranoid CVSS score: 6.4

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).