* [CVE-2026-98316][MODERATE REGULAR] ALSA: bcd2000: Fix race between rawmidi and disconnect [ Upstream
@ 2026-10-10 2:54 21% AL-KERNEL
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From: AL-KERNEL @ 2026-10-10 2:54 UTC (permalink / raw)
To: kernel-cve
CVE: CVE-2026-98316
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: ALSA: bcd2000: Fix race between rawmidi and disconnect [ Upstream
Commit: 3b824930259d54f5047ce6b5c97bd20db2fc2b98
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=3b824930259d54f5047ce6b5c97bd20db2fc2b98
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98316
Analysis date: Fri, 09 Oct 2026 22:54:38 -0400
ActionableScore: 0
ActionableScore lower bound: unknown
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-2026-98316 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98316
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.
======================================================================
AL-KERNEL CLASSIFICATION RESULT
======================================================================
CVE-2026-98316 MODERATE https://www.kernelcve.org/list/?q=CVE-2026-98316 CHECK WITH IMPACT FROM ORIG NN MODERATE | AEGIS IMPACT MODERATE_KPANIC AEGIS_AS=0 LEGACY=MODERATE RESULT=DIFF (independent 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:H/PR:L/UI:N/S:U/C:H/I:H/A:H';*CWE-416;CWE-362;CWE-667;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:H';BEST CVSS score: '7';DESCR 'A race in the ALSA bcd2000 driver can allow an in flight rawmidi trigger or completion callback to access a USB URB while disconnect handling poisons and frees that URB. This creates a kernel use after free condition that can at least cause a kernel crash and local denial of service. Reuse of the freed URB memory may also permit corruption of kernel state, so confidentiality and integrity impact and local privilege escalation cannot be excluded without deeper analysis. For the CVSS the PR:L value is used because a local user or process must have access to the affected ALSA rawmidi device, while AC:H reflects the need to win a timing race with USB disconnect. The issue is not network reachable and requires the affected Behringer BCD2000 USB device and its driver to be present. Impact is at least a local denial of service via kernel crash and in the worst case may include confidentiality or integrity impact due to use after free memory access.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 0) MAYBE LOCK USB INIT RACE UAF HARDWARE LINUS DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN4 - - checked
======================================================================
ACTIONABLESCORE ANALYSIS
======================================================================
ActionableScore=0
PrimitiveClass=CLASS_B
RealUAF=YES
HostAdminRequired=UNKNOWN
NamespaceScopedPrivilege=NO
ImportantCandidate=NO
ManualReview=RECOMMENDED
AutoDowngradeAllowed=YES
RequiresHostUID0=UNKNOWN
AuthorizationDecisionBypass=NO
ProtectedResourceImpact=NONE
B4PendingReview=NO
B4PendingConfirmed=NO
1. ActionableScore
* Raw conservative score: 0.
* Conservative score: 0.
* Raw paranoid score: 0.
* Paranoid score: 0.
* No floor or cap was applied. The real-UAF floors do not apply because this is a constrained USB-disconnect race involving a fixed URB reference, with no demonstrated reclaim or post-free attacker-controlled state.
* Final recommended bucket: **Ordinary Moderate**::
2. Signal breakdown
Positive signals:
* +2 Real UAF or active lifetime violation. Disconnect can free an URB while an already running rawmidi callback still accesses or submits that exact URB.
* +1 Reliable kernel crash or strong DoS. Using a freed URB in the USB submission path can realistically produce an Oops or kernel crash.
Negative signals:
* -1 Hard one-shot teardown race. The rawmidi operation must already be in flight during USB disconnect, which is an externally timed teardown transition.
* -2 Rare physical hardware requirement. The vulnerable path requires the specific Behringer BCD2000 USB device, its ALSA driver, and a device-disconnect event.
Not awarded:
* No local-unprivileged bonus because the supplied evidence does not establish rawmidi device permissions or that one below-host-admin actor controls the complete trigger.
* No structured stale-object leverage. Although an URB is structured, no attacker-controlled reclaim, replacement contents, callback control, or useful post-free field manipulation is established.
* No active lifetime-manipulation bonus. Repeated attacker control over allocation, freeing, and reuse of the URB is not demonstrated.
* No strong or weak LPE bonus. The prior CVSS suggestion of possible confidentiality or integrity impact does not establish an exploitation primitive.
* No confidentiality or integrity bonus. There is no disclosure, directed write, protected-state modification, or demonstrated privilege escalation.
* No repeated-release or refcount bonus. The patch does not show a second free, put, or refcount mutation through the dangling URB.
* No additional Availability point because the potential kernel crash is already counted.
* No remote-reachability bonus. This path is not network-triggerable.
* NEW52 B5-R does not apply. There is no retry-accumulated heap OOB write.
* NEW53 B3-PENDING does not apply. There is no shared-backing write.
* NEW54 B4-PENDING does not apply. No authorization decision is changed from DENY to ALLOW.
Repeated-release checks:
* First operation can end lifetime: usb_free_urb can end the URB lifetime.
* Exact reference survives for concurrent use: yes, an in-flight rawmidi operation may retain or reload the same URB pointer.
* Second lifetime or refcount mutation: no. The stale operation is URB access or submission, not a demonstrated second release.
* Concrete repeated-release bonus: not awarded.
* Paranoid repeated-refcount bonus: not awarded.
* FLOOR 5: not applied.
3. Reachability analysis
A process must access the ALSA rawmidi interface for an attached BCD2000 device while USB disconnect handling runs concurrently. The patch establishes the callback and disconnect race, but it does not establish the device-node permissions or prove that an ordinary user can exercise the complete sequence.
Host-admin privilege is therefore UNKNOWN rather than YES or NO. Numeric UID 0 is not shown to be required. No user-namespace or network-namespace capability participates in the path, so NamespaceScopedPrivilege is NO.
The affected hardware and driver must already be present. A physical disconnect, device disappearance, or equivalent USB teardown is also required. The actor controlling rawmidi may not be the actor controlling disconnect, so complete below-host-admin reachability is unresolved. The timing is materially constrained because the callback must remain in flight across teardown.
4. Primitive and severity interpretation
The exact primitive is a race-driven use-after-free of a USB URB. The disconnect path poisons and frees the URB while a parallel rawmidi trigger or completion path can still access it.
This is best treated as fixed stale driver storage used during asynchronous teardown, rather than an attacker-controlled active-object replacement primitive. The stale operation may pass the URB into active USB processing, but no controlled reclaim, attacker-shaped replacement object, arbitrary read or write, callback hijack, or repeated lifetime mutation is established.
PrimitiveClass is CLASS_B because the lifetime violation is concrete. The demonstrated practical consequence is kernel instability or local DoS. Confidentiality impact, integrity impact, and privilege escalation remain theoretical and unsupported by an independent mechanism.
ImportantCandidate is NO because the evidence matches the constrained USB teardown UAF profile. AutoDowngradeAllowed is YES because no meaningful unresolved reuse, write, disclosure, authorization, or repeated-release primitive remains. Manual review is still recommended to verify whether `bcd2000_midi_send()` or `usb_submit_urb()` consumes exploitable URB fields after allocator reuse, but that possibility is not scored.
5. One-sentence report phrase
A disconnect race in the ALSA bcd2000 driver can let an in flight rawmidi callback access a freed USB URB and crash the kernel, but no controlled reclaim, arbitrary memory access, or privilege escalation primitive is established.
6. Manual review recommendation
MANUAL CHECK RECOMMENDED
Confirm the complete stale-use path through `bcd2000_midi_send()` and `usb_submit_urb()`, along with actual rawmidi permissions, but current evidence supports a constrained hardware-specific crash-capable UAF rather than an Important-grade exploitation primitive.
7. Call-site confidence
Call-site confidence: medium
======================================================================
UPSTREAM PATCH SUMMARY
======================================================================
Patch: ALSA: bcd2000: Fix race between rawmidi and disconnect [ Upstream
Commit: 3b824930259d54f5047ce6b5c97bd20db2fc2b98
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=3b824930259d54f5047ce6b5c97bd20db2fc2b98
Changed files:
sound/usb/bcd2000/bcd2000.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=3b824930259d54f5047ce6b5c97bd20db2fc2b98
======================================================================
DETAILED REPORT METHODOLOGY
======================================================================
The original Linux kernel CVE announcement for CVE-2026-98316 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98316
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:L/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:H
The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
The Best / paranoid CVSS score: 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: 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 [email protected] (and both
send reply to CVE record itself too and see "reply" button below for howto reply).
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