[CVE-2026-98933][LOW] usb: hub: use shorter 120ms post resume hold for SS root hubs

[CVE-2026-98933][LOW] usb: hub: use shorter 120ms post resume hold for SS root hubs

[AL-KERNEL]

CVE: CVE-2026-98933
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: usb: hub: use shorter 120ms post resume hold for SS root hubs
Commit: e4df763ba3c4fdd1d9256f7a75a17ab7c5e31db6
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=e4df763ba3c4fdd1d9256f7a75a17ab7c5e31db6
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98933
Analysis date: Tue, 27 Oct 2026 02:45:00 -0400
ActionableScore: 1
ActionableScore lower bound: unknown
Actionable bucket: Ordinary Moderate
Manual review required: NO

Summary:
Repeated USB3 root-hub runtime-resume polling can crash affected AMD systems due to an excessive post-resume hold, with no demonstrated memory-corruption or authorization primitive.

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

The original Linux kernel CVE announcement for CVE-2026-98933 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98933

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.

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AL-KERNEL CLASSIFICATION RESULT
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CVE-2026-98933	LOW	https://www.kernelcve.org/list/?q=CVE-2026-98933 CHECK WITH IMPACT FROM ORIG NN MODERATE | AEGIS IMPACT MODERATE_KPANIC AEGIS_AS=1 LEGACY=LOW RESULT=DIFF TEMP_DISTANCE_MERGE_SKIP=AEGIS_NO_POSITIVE_SEVERITY_EVIDENCE (final Legacy and Aegis differ; FINAL: LOW, Aegis: MODERATE_KPANIC)	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H';**CWE-400;CWE-754;BEST CVSS score: '4.7';DESCR 'A USB3 root hub runtime PM timing issue can trigger crashes on affected AMD platforms because every resume keeps a runtime PM reference for 200 ms. Repeated polling by a local Android adb process can wake the USB subsystem about once per second until the platform failure occurs. For the CVSS the PR:L value is selected because reliable triggering requires a local process with access to adb or an equivalent USB polling path. AC:H reflects the affected hardware dependency and the need for repeated suspend and resume timing rather than a single deterministic request. The demonstrated impact is availability loss. There is no evidence of UAF, OOB access, information disclosure, arbitrary write, or privilege escalation. Automated impact decision path. The original SimpleNet classifier selected MODERATE_KPANIC. The primary LLM estimated paranoid CVSS 4.7 and the production ActionableScore returned 1 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 LOW because KP specialist did not establish a qualifying panic and 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_CIANNH and DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3 and KPANIC_UNSUPPORTED_REMOVED and V64_AEGIS_UNSUPPORTED_PROMOTION_BLOCKED. The independent weaker Aegis shadow evaluated CVSS 2.5 and ActionableScore 1 with primitive class CLASS_C and manual review REQUIRED. Its independently reconciled impact was MODERATE_KPANIC. The models disagreed but the aggregation rules retained the production result. The final reported impact is LOW.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 1)	MAYBE	DANGER USB SIMPLEFIX HARDWARE LINUS DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS_AND_CIANNH DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3 KPANIC_UNSUPPORTED_REMOVED V64_AEGIS_UNSUPPORTED_PROMOTION_BLOCKED	-	-	checked

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

ActionableScore=1
PrimitiveClass=CLASS_C
RealUAF=NO
HostAdminRequired=UNKNOWN
NamespaceScopedPrivilege=UNKNOWN
ImportantCandidate=NO
ManualReview=NO
AutoDowngradeAllowed=YES
RequiresHostUID0=UNKNOWN
AuthorizationDecisionBypass=NO
ProtectedResourceImpact=NONE
B4PendingReview=NO
B4PendingConfirmed=NO

1. ActionableScore

* Raw base score: 1.
* Conservative score: 1; no floor or cap applied.
* Raw paranoid score: 1.
* Paranoid score: 1; no technically supported stronger primitive.
* Final recommended bucket: **Ordinary Moderate**::

2. Signal breakdown

* +1 Reliable crash/strong DoS: the commit reports crashes on affected AMD platforms after repeated adb polling wakes the USB subsystem.
* +0 Local trigger: polling is described, but the complete access and privilege requirements are not established well enough for an unprivileged-trigger bonus.
* No timing penalty: repeated resume cycles and hardware dependence are shown, but not a narrow, one-shot, externally uncontrollable race.
* No hardware penalty: affected AMD hardware is platform-specific, but uncommon or physical-only hardware access is not established.
* No UAF, OOB access, overwrite, shared-backing write, authorization bypass, disclosure, or integrity primitive is shown.
* B5-R does not apply: there is no heap OOB write, accumulating index, or later consumption of corrupted structured state.
* No extra availability point: it would duplicate the reported crash.

3. Reachability analysis

A local adb or equivalent polling process can repeatedly wake USB runtime PM, but its exact credentials and device-access requirements are not supplied. Host-administrator necessity and namespace-scoped reachability therefore remain unknown. The trigger requires an affected AMD platform, USB3 root-hub runtime suspend/resume activity, and repeated polling. No separate privileged setup, special physical attacker, or difficult race is proven.

4. Primitive and severity reading

The patch only reduces the USB3 root-hub post-resume hold from 200 ms to 120 ms to mitigate a platform compatibility/timing failure. This is a Class C availability issue, not memory or active-state corruption. The shown effect is crashes; the underlying platform failure mechanism and whether every crash is host-wide are not detailed. There is no leverage past availability, so ImportantCandidate is NO and automatic Moderate/Low-like handling is allowed.

5. One-sentence report phrase

Repeated USB3 root-hub runtime-resume polling can crash affected AMD systems due to an excessive post-resume hold, with no demonstrated memory-corruption or authorization primitive.

6. Manual review advice

NO MANUAL CHECK NEEDED

The evidence supports only a hardware-dependent availability issue addressed by a timing adjustment.

7. Call-site confidence

Call-site confidence: medium

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

Patch: usb: hub: use shorter 120ms post resume hold for SS root hubs
Commit: e4df763ba3c4fdd1d9256f7a75a17ab7c5e31db6
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=e4df763ba3c4fdd1d9256f7a75a17ab7c5e31db6

Commit description:

Holding a USB3 hub PM runtime reference for 200ms at hub resume triggers
an AMD platform issue.  Users running Android adb report crashes after
adb has been polling and waking up the USB subsystem once a second for
some time.  Vendors are working on a solution.  Disabling USB runtime PM
is one way to prevent this issue, but it is also proven that reducing the
hold time to 120ms in resume also mitigates it.  See Link for more
details.

Reducing the hold time to 120ms for the USB3 roothub is in itself a valid
change and optimization, as the current 200ms is excessive: a root hub
has no upstream suspended hub whose wake propagation needs to be
accounted for, but still need some time for USB3 link training to
complete.

Keep the 200ms hold for external hubs that commit 8f5b7e2
("usb: hub: fix detection of high tier USB3 devices behind suspended
hubs") is intended for.

Reported-by: Mathieu Fluhr <mathieu.fluhr@gmail.com>
Link: https://lore.kernel.org/all/CAPyJwA_D9qw0T72f8zwM1yKjP+To=maVANbcdsWM7yRmbBxYvw@mail.gmail.com/
Cc: stable <stable@kernel.org>
Fixes: 8f5b7e2 ("usb: hub: fix detection of high tier USB3 devices behind suspended hubs")
Signed-off-by: Lovekesh Solanki <lovekeshsolanki00@gmail.com>
Acked-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Link: https://patch.msgid.link/20260903112903.542719-1-lovekeshsolanki00@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  drivers/usb/core/hub.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=e4df763ba3c4fdd1d9256f7a75a17ab7c5e31db6

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

The original Linux kernel CVE announcement for CVE-2026-98933 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98933

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:H/PR:L/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS score: 4.7

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: unknown
  Paranoid ActionableScore: 1

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).