[CVE-2026-100079][LOW] usb: typec: ucsi: unregister debugfs entries on teardown [ Upstream

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

CVE: CVE-2026-100079
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: usb: typec: ucsi: unregister debugfs entries on teardown [ Upstream
Commit: fb7393519908befdc094be4ea913f582adbf2f7c
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=fb7393519908befdc094be4ea913f582adbf2f7c
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-100079
Analysis date: Fri, 25 Sep 2026 10:09:26 -0400
ActionableScore: 0
ActionableScore lower bound: unknown
Actionable bucket: Ordinary Moderate
Manual review required: NO

Summary:
No one-sentence report phrase was found.

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

The original Linux kernel CVE announcement for CVE-2026-100079 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-100079

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.

======================================================================
AL-KERNEL CLASSIFICATION RESULT
======================================================================

CVE-2026-100079	LOW	https://www.kernelcve.org/list/?q=CVE-2026-100079 CHECK WITH IMPACT FROM ORIG NN MODERATE	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:N';*CWE-772;CWE-459;CWE-404;Other CVSS 'AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:N';BEST CVSS score: '0';DESCR 'UCSI debugfs entries were retained after ucsi_unregister and could remain present when a remote processor restart caused the same UCSI instance to be registered again. This resulted in an already exists debugfs directory error and stale debugfs state. The issue is a debug and lifecycle cleanup problem. It does not provide a demonstrated memory corruption primitive, privilege escalation path, information disclosure, or denial of service condition. Network reachability is not applicable.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 0)	YES	USB INIT SIMPLEFIX DEBUGFS LINUS  DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_GUESSCVSS	YES	NO	checked

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

ActionableScore=0
PrimitiveClass=NONE
RealUAF=NO
HostAdminRequired=UNKNOWN
NamespaceScopedPrivilege=UNKNOWN
ImportantCandidate=NO
ManualReview=NO
AutoDowngradeAllowed=YES

1. ActionableScore

* Raw conservative score: 0
* Conservative score: 0
* Raw paranoid score: 0
* Paranoid score: 0
* Final recommended bucket: **Ordinary Moderate**::

No floor or cap applies. The patch establishes a debugfs lifecycle cleanup issue, not a security primitive.

2. Signal breakdown

* +0 No kernel memory corruption is established. The patch does not show a stale pointer dereference, UAF, double free, refcount mutation, OOB access, or invalid write.
* +0 No reliable kernel crash or broader denial of service is established. The observed symptom is failure to create an already existing debugfs directory after UCSI re-registration.
* +0 No concrete persistent resource leak signal is awarded. The debugfs allocation is retained until ucsi_destroy rather than shown to be permanently unreachable or indefinitely accumulating under normal lifecycle handling.
* +0 No local unprivileged trigger is established. The supplied context does not establish which actor can initiate the complete UCSI unregister and remoteproc restart sequence.
* +0 No remote reachability is established. The affected operation is UCSI driver teardown and registration, not processing of attacker supplied network traffic.
* +0 No confidentiality or integrity signal is awarded. No disclosure path, protected-state modification, authorization bypass, or cross-boundary effect is shown.
* +0 No availability signal is awarded. The duplicate debugfs directory diagnostic does not itself demonstrate device failure, kernel stall, panic, or host-wide service loss.
* +0 No UAF classification is applied. Clearing ucsi->debugfs after kfree prevents a stale pointer from being retained, but the supplied patch does not establish that a later path dereferences that freed pointer.

Important non-awarded signals:

* Controlled reclaim, arbitrary write, callback control, and object replacement are not demonstrated.
* Concrete repeated release or refcount mutation is not demonstrated.
* Structured stale-object leverage is not demonstrated.
* Privilege escalation is not demonstrated.
* A security-boundary bypass is not demonstrated.
* A repeatable kernel resource exhaustion condition is not demonstrated.

3. Reachability analysis

The affected flow occurs when a UCSI instance is unregistered and later registered again, such as across a remoteproc restart in ucsi_glink.

The supplied patch does not establish whether an ordinary local user, a namespace-scoped actor, a delegated service, or a host administrator can initiate the full remoteproc restart and UCSI lifecycle sequence. Therefore HostAdminRequired and NamespaceScopedPrivilege are both UNKNOWN.

Remoteproc restart support and the relevant UCSI hardware or platform configuration may be prerequisites, but the patch does not establish them as attacker controllable or attacker reachable. There is no network-triggered path in the supplied evidence.

4. Primitive and severity interpretation

The exact issue is incomplete cleanup of per-instance debugfs entries during ucsi_unregister. The retained debugfs directory can conflict with a later ucsi_register call for the same UCSI instance, producing an already exists diagnostic and stale debugfs registration state.

This is neither an active structured-object UAF nor fixed stale storage accessed after free. The patch adds debugfs cleanup during unregister and clears the debugfs pointer after freeing its associated allocation. This is defensive lifecycle hygiene, but the supplied evidence does not show a dereference, release, refcount operation, callback invocation, or other active use through the freed pointer.

PrimitiveClass is NONE. The demonstrated consequence is debugfs registration failure or diagnostic logging during a re-registration sequence. Speculative consequences such as a later NULL dereference or UAF are not scored because no relevant call path is supplied. ImportantCandidate is NO and AutoDowngradeAllowed is YES because no meaningful unresolved corruption, ownership, authorization, or security-boundary primitive remains.

Likely operational severity is non-security functional correctness. It can affect debug visibility for a UCSI instance after restart, but it does not establish confidentiality, integrity, availability, or privilege impact.

5. One-sentence report phrase

The UCSI driver failed to remove per-instance debugfs entries during unregister, causing duplicate debugfs directory errors after remoteproc restart and re-registration, with no demonstrated security impact.

6. Manual review recommendation

NO MANUAL CHECK NEEDED

The patch addresses debugfs cleanup and stale registration state only. No concrete memory corruption, authorization bypass, resource exhaustion, kernel crash, or attacker-controlled trigger is established.

7. Call-site confidence

Call-site confidence: medium

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

Patch: usb: typec: ucsi: unregister debugfs entries on teardown [ Upstream
Commit: fb7393519908befdc094be4ea913f582adbf2f7c
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=fb7393519908befdc094be4ea913f582adbf2f7c

Changed files:
  drivers/usb/typec/ucsi/debugfs.c
  drivers/usb/typec/ucsi/ucsi.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=fb7393519908befdc094be4ea913f582adbf2f7c

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

The original Linux kernel CVE announcement for CVE-2026-100079 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-100079

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:L/UI:N/S:U/C:N/I:N/A:N
  The Best / paranoid CVSS vector: AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:N
  The Best / paranoid CVSS score: 0

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: unknown
  Paranoid ActionableScore: 0

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).