[CVE-2026-98086][MODERATE REGULAR] ALSA: ump: do not touch legacy_rmidi before it exists [ Upstream

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

CVE: CVE-2026-98086
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: ALSA: ump: do not touch legacy_rmidi before it exists [ Upstream
Commit: 1c8e01792adf91879322f1ad752f1814de8b7e7d
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=1c8e01792adf91879322f1ad752f1814de8b7e7d
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98086
Analysis date: Fri, 25 Sep 2026 13:47:57 -0400
ActionableScore: 2
ActionableScore lower bound: 1
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-2026-98086 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98086

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-2026-98086	MODERATE	https://www.kernelcve.org/list/?q=CVE-2026-98086 CHECK WITH IMPACT FROM ORIG NN LOW	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:P/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H';**CWE-476;CWE-362;CWE-665;Other CVSS 'AV:P/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '4.6';DESCR 'An ALSA UMP endpoint message can reach the legacy rawmidi naming helpers after endpoint parsing has been marked complete but before legacy_rmidi has been created and attached. If a UMP packet arrives through snd_ump_receive during this initialization window, ump_legacy_set_rawmidi_name can pass a field derived from a NULL rawmidi pointer to snprintf and trigger a kernel fault in IRQ context. For the CVSS the PR:N value is used because an attacker controlling an attached UMP endpoint does not need a local account or privileges on the target system. The issue is not network reachable through the ordinary network stack and normally requires control of a physically connected or otherwise hardware backed MIDI UMP endpoint. Impact is denial of service through a kernel Oops or panic. The shown code provides no UAF, information leak, OOB access, or write primitive into valid kernel memory that would support privilege escalation.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 2) 	MAYBE	KASAN NULLPTR SIMPLEFIX HARDWARE LINUS PACKET  INCREASED_FROM_LOW_BASED_ON_REQUIREMANUALCHECK DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN4	-	-	checked

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

ActionableScore=2
ActionableScoreLower=1
PrimitiveClass=CLASS_C
RealUAF=NO
HostAdminRequired=NO
NamespaceScopedPrivilege=NO
ImportantCandidate=NO
ManualReview=RECOMMENDED
AutoDowngradeAllowed=YES

1. ActionableScore

* Raw conservative score: 1
* Conservative score: 1
* Raw paranoid score: 2
* Paranoid score: 2
* No floor or cap was applied.
* Final recommended bucket: **Ordinary Moderate**::

2. Signal breakdown

Conservative signals:

* +1 Firmware or device mediated external influence. A UMP endpoint controls the packet delivered through `snd_ump_receive()`.
* +1 Reliable kernel crash or strong DoS. `snprintf()` receives a destination derived from a NULL `legacy_rmidi` pointer in IRQ context, with a KASAN NULL-pointer dereference already observed.
* -1 Narrow hardware timing. The packet must arrive during the initialization window after `parsed` is set but before `legacy_rmidi` is attached.

Paranoid adjustment:

* The -1 timing penalty is withheld because a deliberately programmed endpoint may be able to send packets promptly and repeatedly during device initialization.

Not awarded:

* No UAF exists. The rawmidi object has not yet been created or attached rather than having been freed.
* No valid-memory overwrite, controlled target, controlled reclaim, OOB access, disclosure, repeated release, or refcount mutation is established.
* No C or I impact and no privilege-escalation leverage are demonstrated.
* No remote-network bonus applies.
* No additional Availability point is awarded because it would double-count the same crash.
* No physical or rare-hardware penalty is applied because the supplied evidence does not prove that every affected UMP transport requires uncommon hardware.

3. Reachability analysis

The supported attacker model is a malicious or malfunctioning UMP endpoint capable of delivering an endpoint-name packet during device initialization. Such an endpoint does not require a host account or host-administrator privilege, so `HostAdminRequired=NO`.

Ordinary local-user software injection is not established. The path is not directly network reachable, and no namespace capability participates in the trigger. Device attachment and driver probing can occur automatically, but control of a suitable endpoint is required. The conservative analysis treats the initialization window as narrow. The paranoid analysis recognizes that endpoint firmware may influence packet timing across repeated enumeration attempts.

4. Primitive and severity interpretation

The exact primitive is a NULL-derived destination passed to `snprintf()`, producing an invalid low-address write attempt and immediate kernel fault. This is an initialization-order logic race and Class C crash behavior, not stale storage, UAF, or active-object lifetime corruption.

There is no first lifetime-ending operation, surviving dangling reference, or second release/refcount mutation. The demonstrated consequence is kernel Oops or panic. Privilege escalation and useful memory corruption remain unsupported theoretical outcomes.

`ImportantCandidate=NO` because no independently useful corruption, ownership, authorization, or lifetime primitive survives after excluding the crash. `AutoDowngradeAllowed=YES` because the issue is a constrained NULL dereference with no unresolved Class A or Class B leverage.

5. One-sentence report phrase

A malicious or malfunctioning ALSA UMP endpoint can deliver a packet before legacy rawmidi initialization completes and trigger a NULL-pointer dereference in IRQ context, causing a host kernel denial of service.

6. Manual review recommendation

MANUAL CHECK RECOMMENDED

Confirm which UMP transport drivers can deliver packets during this window and whether any software-only, remotely mediated, or ordinary local-user injection path exists.

7. Call-site confidence

Call-site confidence: medium

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

Patch: ALSA: ump: do not touch legacy_rmidi before it exists [ Upstream
Commit: 1c8e01792adf91879322f1ad752f1814de8b7e7d
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=1c8e01792adf91879322f1ad752f1814de8b7e7d

Changed files:
  sound/core/ump.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=1c8e01792adf91879322f1ad752f1814de8b7e7d

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

The original Linux kernel CVE announcement for CVE-2026-98086 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98086

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:H
  The Best / paranoid CVSS vector: AV:P/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS score: 4.6

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: 1
  Paranoid ActionableScore: 2

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 alexanjelausa@gmail.com (and both
send reply to CVE record itself too and see "reply" button below for howto reply).