* [CVE-2026-99038][LOW] memstick: rtsx_usb_ms: complete requests after eject instead of dropping them
@ 2026-10-27 1:16 21% AL-KERNEL
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From: AL-KERNEL @ 2026-10-27 1:16 UTC (permalink / raw)
To: kernel-cve
CVE: CVE-2026-99038
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: memstick: rtsx_usb_ms: complete requests after eject instead of dropping them
Commit: f2c181e1d58e911804e14543b2f1cc6b23a0d4d6
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=f2c181e1d58e911804e14543b2f1cc6b23a0d4d6
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99038
Analysis date: Mon, 26 Oct 2026 21:16:54 -0400
ActionableScore: 0
ActionableScore lower bound: unknown
Actionable bucket: Ordinary Moderate
Manual review required: NO
Summary:
A narrow physical device-removal race can drop a Memory Stick request completion and indefinitely stall driver teardown without evidence of memory corruption or authorization impact.
======================================================================
ABOUT THIS REPORT
======================================================================
The original Linux kernel CVE announcement for CVE-2026-99038 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99038
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-2026-99038 LOW https://www.kernelcve.org/list/?q=CVE-2026-99038 CHECK WITH IMPACT FROM ORIG NN MODERATE | AEGIS IMPACT MODERATE_KPANIC AEGIS_AS=0 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:P/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H';CWE-362;CWE-667;CWE-404;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 between memstick_check and rtsx_usb_ms_drv_remove can leave a request accepted by the memstick core but never processed or completed. Triggering requires device eject or removal in a narrow window after the removing check and before request handling, which can block memstick_check and memstick_remove_host indefinitely. For the CVSS the PR:N value reflects physical device removal that needs no authenticated system privilege, while software initiated driver removal normally requires administrative control. The demonstrated primitive is a lost request completion and wait hang with no evidence of UAF, OOB access, information disclosure, or privilege escalation. Availability impact is normally limited to device removal and related worker activity, although prolonged workqueue blockage can cause broader subsystem disruption. Automated impact decision path. The original SimpleNet classifier selected MODERATE_KPANIC. The primary LLM estimated paranoid CVSS 4.2 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 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 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 2.0 and ActionableScore 0 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 0) MAYBE LOCK USB INIT RACE UAF HARDWARE LINUS DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3 KPANIC_UNSUPPORTED_REMOVED V64_AEGIS_UNSUPPORTED_PROMOTION_BLOCKED - - checked
======================================================================
ACTIONABLESCORE ANALYSIS
======================================================================
ActionableScore=0
PrimitiveClass=CLASS_C
RealUAF=NO
HostAdminRequired=NO
NamespaceScopedPrivilege=NO
ImportantCandidate=NO
ManualReview=NO
AutoDowngradeAllowed=YES
RequiresHostUID0=NO
AuthorizationDecisionBypass=NO
ProtectedResourceImpact=NONE
B4PendingReview=NO
B4PendingConfirmed=NO
1. ActionableScore
* Raw base score: -2.
* Conservative score: 0 after clamping the negative raw score to the 0–10 range.
* Raw paranoid score: -2.
* Paranoid score: 0 after the same clamp; no separate technically supported impact exists.
* Final recommended bucket: **Ordinary Moderate**::
2. Signal breakdown
* +1 Reliable DoS: a request accepted just before eject can be dropped without completion, indefinitely blocking `memstick_check()` and device removal work.
* -1 Hard race: the trigger requires the narrow interval between `memstick_check()` passing its removal check and eject/removal or cancellation of queued work.
* -2 Physical/specialized-device exposure: the below-host-admin path requires access to and removal/ejection of a Realtek USB Memory Stick device. Software-driven driver removal ordinarily requires administration.
* No extra availability point: blocked workers and stalled removal are consequences of the same lost-completion hang.
* No UAF, OOB access, overwrite, stale-object consumption, authorization bypass, disclosure, or integrity primitive is shown.
* NEW52 B5-R does not apply: there is no heap OOB write, retry-accumulated index, or later consumption of corrupted structured state.
* NEW53/B3 and NEW54/B4 do not apply: neither shared-backing modification nor a DENY-to-ALLOW authorization change exists.
3. Reachability analysis
A person with physical access can unplug/eject the specialized USB device without host credentials, so host-administrator power and UID 0 are not required for that trigger. Software unbind/removal is generally administrative but is not needed for the physical path. No namespace capability, prior delegation, or remote path is implicated. The race is explicitly narrow and tied to removal timing.
4. Primitive and severity reading
The primitive is a lost request completion causing indefinite waiting during teardown, classified CLASS_C. It is synchronization/availability failure rather than memory corruption or lifetime misuse. The demonstrated effect is stalled device removal and blocked workqueue activity; host panic, persistent system-wide outage, and security-boundary effects are unproven. Important retention is therefore unwarranted, and automatic downgrade is safe.
5. One-sentence report phrase
A narrow physical device-removal race can drop a Memory Stick request completion and indefinitely stall driver teardown without evidence of memory corruption or authorization impact.
6. Manual review advice
NO MANUAL CHECK NEEDED
The patch and call path establish only a constrained lost-completion hang.
7. Call-site confidence
Call-site confidence: high
======================================================================
UPSTREAM PATCH SUMMARY
======================================================================
Patch: memstick: rtsx_usb_ms: complete requests after eject instead of dropping them
Commit: f2c181e1d58e911804e14543b2f1cc6b23a0d4d6
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=f2c181e1d58e911804e14543b2f1cc6b23a0d4d6
Commit description:
memstick_check() can pass its host->removing check just before
rtsx_usb_ms_drv_remove() sets eject/removing. Its next request is then
silently dropped: rtsx_usb_ms_request() skips schedule_work() once eject
is set, and drv_remove's cancel_work_sync() can also cancel a queued
handle_req before it picks the request up. Nobody completes
card->mrq_complete.
Once memstick core waits for requests without a timeout ("memstick: core:
wait for request completion before freeing card"), this hangs removal:
memstick_check() never returns and memstick_remove_host() blocks in
flush_workqueue():
INFO: task kworker/u10:3:65 blocked for more than 20 seconds.
Workqueue: kmemstick memstick_check
__wait_for_common
memstick_check
INFO: task kworker/1:1:33 blocked for more than 20 seconds.
Workqueue: usb_hub_wq hub_event
__flush_workqueue
memstick_remove_host
rtsx_usb_ms_drv_remove
Never drop a request. rtsx_usb_ms_request() always schedules handle_req,
and handle_req fails requests with -ENOMEDIUM once eject is set, without
touching the device. drv_remove flushes handle_req instead of cancelling
it, and cancels it only after memstick_remove_host(), when no new
request can arrive, so it cannot run on a freed host.
The host_mutex drain in drv_remove is removed: handle_req always leaves
host->req NULL when it finishes, so the drain never had anything to do,
and it would now race with handle_req.
Fixes: 99451dc ("memstick: Add realtek USB memstick host driver")
Cc: [email protected]
Link: https://lore.kernel.org/all/[email protected]/
Signed-off-by: Nguyen Ngoc Thang <[email protected]>
Signed-off-by: Ulf Hansson <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
Changed files:
drivers/memstick/host/rtsx_usb_ms.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=f2c181e1d58e911804e14543b2f1cc6b23a0d4d6
======================================================================
DETAILED REPORT METHODOLOGY
======================================================================
The original Linux kernel CVE announcement for CVE-2026-99038 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99038
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: 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 [email protected] (and both
send reply to CVE record itself too and see "reply" button below for howto reply).
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