[CVE-2026-98945][MODERATE 7.0] HID: steam: Rearrange teardown sequence [ Upstream

[CVE-2026-98945][MODERATE 7.0] HID: steam: Rearrange teardown sequence [ Upstream

[AL-KERNEL]

CVE: CVE-2026-98945
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: HID: steam: Rearrange teardown sequence [ Upstream
Commit: d2587923d50c8b141ce0ccb284c714cf6054d6a7
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=d2587923d50c8b141ce0ccb284c714cf6054d6a7
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98945
Analysis date: Tue, 27 Oct 2026 01:25:41 -0400
ActionableScore: 0
ActionableScore lower bound: unknown
Actionable bucket: Ordinary Moderate
Manual review required: NO

Summary:
A narrow Steam HID teardown race can leave asynchronous work holding a freed `steam_device`, causing a potential kernel crash without a demonstrated controlled corruption primitive.

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

The original Linux kernel CVE announcement for CVE-2026-98945 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98945

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: NO

A detailed explanation of the methodology and priority rules is included
at the end of this message.

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

CVE-2026-98945	MODERATE	https://www.kernelcve.org/list/?q=CVE-2026-98945 CHECK WITH IMPACT FROM ORIG NN LOW | AEGIS IMPACT MODERATE_KPANIC AEGIS_AS=2 LEGACY=MODERATE_KPANIC RESULT=SAME V39_AEGIS_ONE_STEP_UP=MODERATE->MODERATE_KPANIC (final reconciliation agrees; DECISION: both MODERATE_KPANIC)	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-416;CWE-362;CWE-662;Other CVSS 'AV:P/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:H';BEST CVSS score: '6.4';DESCR 'A race in the HID Steam teardown sequence could schedule callbacks or work while cleanup was in progress, leaving them with a dangling pointer to a freed steam_device structure. The resulting primitive is a potential use after free that can cause a kernel crash and may permit corruption of reused kernel memory depending on callback behavior and allocator reuse. Triggering normally requires physical device removal or an equivalent device teardown event with precise callback timing, so AV:P and AC:H are appropriate. For the CVSS the PR:N value is used because physically disconnecting or controlling the peripheral does not require an authenticated local kernel privilege, although software initiated driver unbind normally requires elevated local rights. The base impact is C:L I:L A:H, while the paranoid HHH interpretation reflects the unresolved consequences of callback access to freed kernel memory rather than a proven arbitrary write or privilege escalation path. Automated impact decision path. The original SimpleNet classifier selected MODERATE_KPANIC. The primary LLM estimated paranoid CVSS 6.4 and the production ActionableScore returned 0 with recommendation Ordinary Moderate. The production rules then evaluated CVSS thresholds and ActionableScore thresholds. Recorded rule transitions were ActionableScore thresholds stage MODERATE_KPANIC to MODERATE because the ActionableScore threshold rule was applied. final reconciliation stage MODERATE to MODERATE_KPANIC 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_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN4 and V39_AEGIS_ONE_STEP_UP and MANUAL_REVIEW_REQUIRED. The independent weaker Aegis shadow evaluated CVSS 2.0 and ActionableScore 2 with primitive class CLASS_B and manual review REQUIRED. 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_KPANIC.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 0)	MAYBE	LOCK DANGER USB UAF LINUS PACKET  DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN4 KPANIC V39_AEGIS_ONE_STEP_UP MANUAL_REVIEW_REQUIRED	-	-	checked

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

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

1. ActionableScore

* Raw base score: 0.
* Conservative score: 0.
* Raw paranoid score: 0.
* Paranoid score: 0.
* No score floor applies: this is an asynchronous teardown UAF with physical-device and difficult-timing restrictions, and no material post-reuse primitive is shown.
* Final recommended bucket: **Ordinary Moderate**::

2. Signal breakdown

* +2 — Real UAF: callbacks or queued work can retain `steam` after the `steam_device` has been freed.
* +1 — Plausible kernel crash from asynchronous dereference of the dangling structure.
* -2 — Physical/specialized-device prerequisite: the supported below-host-admin path requires Steam HID hardware removal or equivalent peripheral-controlled teardown.
* -1 — Hard timing: the commit identifies a narrow teardown window; the evidence does not show reliable attacker control of the callback interleaving.
* No extra availability point: it would duplicate the same potential crash.
* No structured stale-object leverage: callback field consumption, attacker-shaped replacement, controlled reclaim, or post-free write contents are not shown.
* No confidentiality, integrity, arbitrary-write, callback-hijack, or LPE point is supported.
* No repeated release/refcount mutation is present; FLOOR 5 therefore does not apply.
* B5-R, B3-PENDING, and B4-PENDING do not apply.

3. Reachability analysis

Physical disconnection or peripheral control can initiate teardown without host UID 0 or host-administrator capability, while software driver unbind would normally require elevated administration. No namespace capability is involved. The affected hardware and precise callback timing are material prerequisites. Repeatable, reliable winning of the teardown window is not established.

4. Primitive and severity reading

The primitive is a real CLASS_B asynchronous lifetime violation involving an active structured `steam_device`, but it occurs during device teardown and the supplied evidence only establishes dangling callback/work access and plausible crash. Moving hardware close earlier, clearing `client_opened` under the lock, and synchronously cancelling work before unregister/final teardown closes the scheduling window. Reuse-based corruption is theoretical, not patch-proven. This is not a second lifetime/refcount mutation and not CLASS_A. ImportantCandidate is NO and auto-downgrade is allowed because no material non-crash leverage or unresolved trust-boundary primitive is shown.

5. One-sentence report phrase

A narrow Steam HID teardown race can leave asynchronous work holding a freed `steam_device`, causing a potential kernel crash without a demonstrated controlled corruption primitive.

6. Manual review advice

MANUAL CHECK RECOMMENDED

Confirm the callback bodies and final allocation/free path, but current evidence supports a constrained physical-device teardown UAF.

7. Call-site confidence

Call-site confidence: medium

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

Patch: HID: steam: Rearrange teardown sequence [ Upstream
Commit: d2587923d50c8b141ce0ccb284c714cf6054d6a7
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=d2587923d50c8b141ce0ccb284c714cf6054d6a7

Changed files:
  drivers/hid/hid-steam.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=d2587923d50c8b141ce0ccb284c714cf6054d6a7

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

The original Linux kernel CVE announcement for CVE-2026-98945 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98945

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:L/I:L/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: 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: YES
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).