[CVE-2026-90031][LOW] usb-storage: ene_ub6250: fix race between scan work and probe

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

CVE: CVE-2026-90031
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: usb-storage: ene_ub6250: fix race between scan work and probe
Commit: 9cd335f4f41e84d1ab88d80150ffee8dee9650d7
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=9cd335f4f41e84d1ab88d80150ffee8dee9650d7
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90031
Analysis date: Wed, 16 Sep 2026 10:48:22 -0400
ActionableScore: 1
ActionableScore lower bound: 0
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-2026-90031 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90031

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-2026-90031	LOW	https://www.kernelcve.org/list/?q=CVE-2026-90031 CHECK WITH IMPACT FROM ORIG NN LOW	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:P/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H';CWE-362;CWE-667;CWE-662;Other CVSS 'AV:P/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '4.2';DESCR 'A race in the ene_ub6250 USB storage probe path can occur because delayed scan work and ene_get_card_type can use the shared current_urb at the same time. The scan path already serializes current_urb with dev_mutex, but the card type probe did not, so usb_submit_urb can warn that the URB is already active if the scan work runs during probe. For the CVSS the PR:N is used for the physical attack model because a person who can attach or emulate the affected USB device does not need an account on the target system. The issue is not network reachable and normally requires physical USB access or an equivalent local USB emulation setup. Impact is primarily denial of service for the USB storage probe path, with possible higher availability impact on systems configured to panic on warnings.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 1)	YES	LOCK USB WARNONLY SIMPLEFIX RACE LINUS SYZBOT 	NO	NO	checked

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

ActionableScore=1
ActionableScoreLower=0
PrimitiveClass=CLASS_C
RealUAF=NO
HostAdminRequired=NO
NamespaceScopedPrivilege=NO
ImportantCandidate=NO
ManualReview=NO
AutoDowngradeAllowed=YES

1. ActionableScore

* Raw conservative score: 0
* Conservative score: 0
* Raw paranoid score: 1
* Paranoid score: 1
* Final recommended bucket: **Ordinary Moderate**::

No floor was applied. No UAF floor applies because no real UAF or post-lifetime object use is established.

2. Signal breakdown

Conservative positive signals:

* +1 Firmware or device mediated external influence. The trigger depends on the affected USB storage device path and on probe or scan behavior mediated through the USB storage stack.
* +1 Limited availability impact. Concurrent use of `us->current_urb` can cause `usb_submit_urb()` to warn that the URB is already active, potentially disrupting the affected USB storage probe path.

Conservative negative signals:

* -2 Physical or equivalent local USB access. The realistic attacker model requires attaching or emulating an affected USB storage device, not remote network traffic or an ordinary local syscall path.

Paranoid additional signal:

* +1 Stronger availability interpretation. On systems configured with panic on warning, the demonstrated WARN path may become a host level crash, but this is configuration dependent.

Important non-awarded signals:

* No RealUAF is awarded. The patch shows concurrent use of a shared URB pointer, not post-lifetime use of a freed object.
* No CLASS_A or CLASS_B primitive is awarded. There is no controlled reclaim, arbitrary write, OOB access, double release, refcount mutation, or active structured stale object use.
* No confidentiality or integrity signal is awarded. The evidence supports warning or DoS behavior only.
* No remote reachability is awarded. This is USB device exposure, not network exposure.
* No extra availability point is awarded for the same warning beyond the paranoid panic on warning interpretation.
* No manual review trigger is present under the supplied rules because this is not memory corruption, not a security boundary bypass, and not a persistent resource or ownership violation.

3. Reachability analysis

The practical trigger requires physical access to plug a suitable USB storage device, or an equivalent local USB emulation setup such as a USB gadget or fuzzing environment. No host administrator account is required for the physical attacker model, so `HostAdminRequired=NO`.

The issue is not namespace scoped. Network namespaces, user namespaces, and container capabilities do not materially define the vulnerable operation.

There is no network attack path. The vulnerable condition occurs during USB storage probe after `usb_stor_probe2()` schedules delayed scan work and before or during `ene_get_card_type()`.

The race requires overlap between delayed scan work and the ENE card type probe, but the supplied evidence from syzbot and the commit demonstrates the race as reachable. I did not apply a separate hard race penalty because the physical access penalty already captures the main practical reachability limitation, and the prompt says not to penalize merely because a race exists.

4. Primitive and severity interpretation

The exact primitive is an improper synchronization race over `us->current_urb`. The scan path uses `us->dev_mutex`, while the ENE card type probe path previously did not.

This is not active structured UAF and not fixed stale storage UAF. It is an invalid concurrent active URB state that can lead to a warning from `usb_submit_urb()`.

There is no concrete repeated release or refcount operation. There is no first lifetime operation that may free an object, no surviving dangling reference, and no second lifetime mutation.

Primitive class is `CLASS_C` because the demonstrated behavior is warning or DoS style invalid state without an independently useful corruption primitive.

Demonstrated consequence is disruption of USB storage probing and a kernel warning. Speculative consequence is host crash only on panic on warning systems.

ImportantCandidate is `NO` because the patch does not establish memory corruption, lifetime corruption, security boundary bypass, or a meaningful unresolved exploitation primitive. AutoDowngradeAllowed is `YES` because automatic downgrade would not discard a concrete Important grade primitive.

Likely operational severity is low or ordinary Moderate, mainly relevant for systems exposed to untrusted physical USB devices or automated USB fuzzing environments.

5. One-sentence report phrase

A race in the ene_ub6250 USB storage probe path can let delayed scan work and card type probing use the shared current_urb concurrently, causing an active URB warning and limited USB storage denial of service, with host crash impact mainly limited to panic on warning configurations.

6. Manual review recommendation

NO MANUAL CHECK NEEDED

Reason: the issue is physical USB or local emulation reachable, has no established UAF or other memory corruption primitive, and the demonstrated impact is warning or limited DoS behavior.

7. Call-site confidence

Call-site confidence: high

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

Patch: usb-storage: ene_ub6250: fix race between scan work and probe
Commit: 9cd335f4f41e84d1ab88d80150ffee8dee9650d7
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=9cd335f4f41e84d1ab88d80150ffee8dee9650d7

Commit description:

ene_ub6250_probe() calls usb_stor_probe2(), which starts the usb-storage
infrastructure and schedules the delayed scan work.  The driver then
calls ene_get_card_type(), which sends an ENE command through
ene_send_scsi_cmd() and the usb-storage bulk transfer helpers.

Both the delayed scan work, through usb_stor_Bulk_max_lun(), and
ene_get_card_type() use us->current_urb.  The scan work serializes this
access with us->dev_mutex, but the ENE card-type probe does not.  If the
scan work runs while ene_get_card_type() is still using us->current_urb,
usb_submit_urb() warns that the URB is already active.

Serialize ene_get_card_type() with us->dev_mutex, matching the locking
used by the scan path.

Reported-by: syzbot+22ea20ef3afb6785b122@syzkaller.appspotmail.com
Cc: stable <stable@kernel.org>
Closes: https://syzkaller.appspot.com/bug?extid=22ea20ef3afb6785b122
Assisted-by: Qwen:Qwen3.6
Signed-off-by: Liu Qi <liuqi@longcheer.com>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Link: https://patch.msgid.link/20260821090416.1247127-1-liuqi@longcheer.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  drivers/usb/storage/ene_ub6250.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=9cd335f4f41e84d1ab88d80150ffee8dee9650d7

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

The original Linux kernel CVE announcement for CVE-2026-90031 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90031

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:L
  The Best / paranoid CVSS vector: AV:P/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS score: 4.2

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: 0
  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).