[CVE-2026-98767][MODERATE REGULAR] usb: dwc3: gadget: fix IRQ storm on invalid event buffer count [ Upstream

[CVE-2026-98767][MODERATE REGULAR] usb: dwc3: gadget: fix IRQ storm on invalid event buffer count [ Upstream

[AL-KERNEL]

CVE: CVE-2026-98767
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: usb: dwc3: gadget: fix IRQ storm on invalid event buffer count [ Upstream
Commit: 96918ca25ff467c25675478fc79393df4ae9d74c
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=96918ca25ff467c25675478fc79393df4ae9d74c
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98767
Analysis date: Mon, 19 Oct 2026 02:24:15 -0400
ActionableScore: 0
ActionableScore lower bound: unknown
Actionable bucket: Ordinary Moderate
Manual review required: NO

Summary:
An invalid DWC3 event count left a level-triggered interrupt uncleared and caused a deterministic IRQ storm followed by kernel panic, but the demonstrated trigger requires host-level raw MMIO access and exposes no memory-corruption or authorization-bypass primitive.

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

The original Linux kernel CVE announcement for CVE-2026-98767 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98767

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: 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-2026-98767	MODERATE	https://www.kernelcve.org/list/?q=CVE-2026-98767 CHECK WITH IMPACT FROM ORIG NN LOW | AEGIS IMPACT MODERATE_KPANIC AEGIS_AS=0 LEGACY=MODERATE RESULT=DIFF V39_AEGIS_ONE_STEP_UP=LOW->MODERATE TEMP_DISTANCE_MERGE_SKIP=AEGIS_LOW_ELIGIBLE_NO_POSITIVE_SIGNAL (final Legacy and Aegis differ; FINAL: MODERATE, Aegis: MODERATE_KPANIC)	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:H';**CWE-400;CWE-755;*CWE-835;BEST CVSS score: '4.4';DESCR 'An invalid DWC3 gadget event count can cause a persistent interrupt storm because dwc3_check_event_buf returns without acknowledging the level triggered interrupt source. The asserted interrupt line can accumulate unhandled interrupts until the generic IRQ code reaches a BUG and panics the kernel. For the CVSS the PR:H value is used because the demonstrated trigger requires direct MMIO access to GEVNTCOUNT through a mechanism such as devmem, which normally requires root or CAP_SYS_RAWIO. The issue is local under the demonstrated conditions and there is no evidence that an ordinary remote USB host can directly write this controller register or reliably produce the invalid count through USB traffic. Impact is denial of service through kernel panic. No memory corruption, information disclosure, or privilege escalation primitive is supported by the analyzed code path. Automated impact decision path. The original SimpleNet classifier selected MODERATE_KPANIC. The primary LLM estimated paranoid CVSS 4.4 and the production ActionableScore returned 0 with recommendation Ordinary Moderate. The production rules then evaluated CVSS thresholds and ActionableScore thresholds. Recorded rule transitions were CVSS and initial triage stage MODERATE_KPANIC to MODERATE because the CVSS score, vector or bug class threshold rule was applied. ActionableScore thresholds stage MODERATE to LOW because the ActionableScore threshold rule was applied. final reconciliation stage LOW to MODERATE because the cross model evidence reconciliation rule was applied. The legacy KP specialist has no review artifact for this run. The legacy FD or DH downgrade specialist has no review artifact for this run. Exact triggered rule markers were DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS and DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3 and V39_AEGIS_ONE_STEP_UP and MANUAL_REVIEW_REQUIRED. The independent weaker Aegis shadow evaluated CVSS 4.5 and ActionableScore 0 with primitive class CLASS_C and manual review NO. Its independently reconciled impact was MODERATE_KPANIC. Cross model aggregation changed the production result under an enabled evidence gated merge rule. The final reported impact is MODERATE.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 0)	MAYBE	OOB LOCK USB INIT ERRORPATH HARDWARE DEBUGFS LINUS DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3 V39_AEGIS_ONE_STEP_UP MANUAL_REVIEW_REQUIRED	-	-	checked

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

ActionableScore=0
PrimitiveClass=CLASS_C
RealUAF=NO
HostAdminRequired=YES
NamespaceScopedPrivilege=NO
ImportantCandidate=NO
ManualReview=NO
AutoDowngradeAllowed=YES
RequiresHostUID0=UNKNOWN
AuthorizationDecisionBypass=NO
ProtectedResourceImpact=NONE
B4PendingReview=NO
B4PendingConfirmed=NO

1. ActionableScore

* Raw conservative score: -1
* Conservative score: 0
* Raw paranoid score: -1
* Paranoid score: 0
* Applied score-range lower bound: -1 -> 0
* Final recommended bucket: **Ordinary Moderate**::

2. Signal breakdown

Positive signals:

* +1 Reliable kernel crash / strong DoS. An uncleared level-triggered interrupt causes an IRQ storm, reaches the unhandled-interrupt threshold, and triggers a kernel BUG and panic.

Negative signals:

* -2 Full host-admin-equivalent privilege. The demonstrated trigger writes directly to the DWC3 MMIO register using `devmem`, which normally requires host-level `CAP_SYS_RAWIO` or equivalent unrestricted hardware access.

Important non-awarded signals:

* No memory-corruption point. The patch establishes no OOB read, OOB write, UAF, stale object, or arbitrary write.
* No remote-reachability point. A USB host cannot directly write `GEVNTCOUNT`, and no USB traffic sequence is shown to make the controller report the invalid count.
* No firmware-mediated external-influence point. Hardware or firmware malfunction is possible, but attacker influence through that route is not established.
* No additional availability point. The IRQ storm and kernel panic are one consequence and are not counted twice.
* No confidentiality, integrity, authorization-bypass, or privilege-escalation signal.
* NEW52 B5-R does not apply because there is no retry-accumulated heap OOB write.
* NEW53 B3-PENDING does not apply because there is no shared-backing write.
* V33 and V34 do not apply because no attacker-influenced active structured-state corruption is established.
* NEW54 B4-PENDING does not apply because no mandatory authorization decision changes from DENY to ALLOW.

3. Reachability analysis

The demonstrated actor is a host administrator or a process with host-level raw MMIO access. The reproducer writes an invalid value directly to `DWC3_BASE + 0xc40c` through `devmem`. This is not a namespace-scoped operation, and an attacker-created user or network namespace does not normally grant access to physical MMIO.

Numeric host UID 0 is not strictly proven as mandatory because a non-UID-0 process could theoretically hold host `CAP_SYS_RAWIO`, so `RequiresHostUID0=UNKNOWN`. Effective host-administrator power is nevertheless established for the demonstrated trigger, so `HostAdminRequired=YES`.

A DWC3 gadget controller and mapped register range are prerequisites. No timing race is required. Once the invalid count is installed, the level-triggered IRQ remains asserted and the panic path is deterministic. Ordinary USB packets, a remote USB host, and an unprivileged local process are not shown to control the register value.

4. Primitive and severity interpretation

The exact primitive is an invalid-state handling failure. `dwc3_check_event_buf()` detects an excessive event count but returns `IRQ_NONE` without acknowledging the level-triggered interrupt source. This creates a persistent IRQ storm until generic IRQ handling invokes a fatal BUG.

This is neither fixed stale storage nor an active structured-object UAF. There is no release, refcount mutation, lifetime violation, active-state corruption, or repeated-release sequence.

The appropriate classification is `CLASS_C` because the demonstrated behavior is a kernel panic without an independently useful corruption primitive. The practical consequence is host denial of service. Stronger consequences such as memory corruption, information disclosure, privilege escalation, or remote USB-triggered panic are unsupported.

`ImportantCandidate=NO` because no Important-preserving primitive or unresolved trust-boundary corruption exists. `AutoDowngradeAllowed=YES` because the complete demonstrated trigger already requires host-admin-equivalent MMIO access and produces only a crash.

5. One-sentence report phrase

An invalid DWC3 event count left a level-triggered interrupt uncleared and caused a deterministic IRQ storm followed by kernel panic, but the demonstrated trigger requires host-level raw MMIO access and exposes no memory-corruption or authorization-bypass primitive.

6. Manual review recommendation

NO MANUAL CHECK NEEDED

The issue is a host-admin-triggered crash-only condition with no demonstrated lower-privilege, remote, corruption, or security-boundary path.

7. Call-site confidence

Call-site confidence: high

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

Patch: usb: dwc3: gadget: fix IRQ storm on invalid event buffer count [ Upstream
Commit: 96918ca25ff467c25675478fc79393df4ae9d74c
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=96918ca25ff467c25675478fc79393df4ae9d74c

Changed files:
  kernel/irq/spurious.c
  drivers/usb/dwc3/core.h
  drivers/usb/dwc3/ep0.c
  drivers/usb/dwc3/gadget.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=96918ca25ff467c25675478fc79393df4ae9d74c

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

The original Linux kernel CVE announcement for CVE-2026-98767 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98767

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: Not available
  The Best / paranoid CVSS vector: AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS score: 4.4

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: 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: 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).