[CVE-2026-98587][LOW] firewire: cdev: fix back-transition for iso_resource_auto client resource [ Upstream

[CVE-2026-98587][LOW] firewire: cdev: fix back-transition for iso_resource_auto client resource [ Upstream

[AL-KERNEL]

CVE: CVE-2026-98587
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: firewire: cdev: fix back-transition for iso_resource_auto client resource [ Upstream
Commit: ee1df60a0d0e8ab4b00137135733bdadd6d33dab
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=ee1df60a0d0e8ab4b00137135733bdadd6d33dab
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98587
Analysis date: Mon, 19 Oct 2026 00:07:53 -0400
ActionableScore: 1
ActionableScore lower bound: unknown
Actionable bucket: Ordinary Moderate
Manual review required: NO

Summary:
A race between FireWire isochronous resource work and file descriptor release can reverse a pending deallocation into reallocation, potentially retaining channel or bandwidth resources without establishing memory corruption or privilege escalation.

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

The original Linux kernel CVE announcement for CVE-2026-98587 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98587

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-2026-98587	LOW	https://www.kernelcve.org/list/?q=CVE-2026-98587 CHECK WITH IMPACT FROM ORIG NN MODERATE | AEGIS IMPACT LOW AEGIS_AS=0 LEGACY=LOW RESULT=SAME (final reconciliation agrees; DECISION: both LOW)	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H';CWE-362;CWE-667;*CWE-664;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '4.7';DESCR 'A race in the FireWire cdev automatic isochronous resource lifecycle can allow iso_resource_auto_work to change the state from ISO_RES_AUTO_DEALLOC back to ISO_RES_AUTO_REALLOC after file descriptor release has requested deallocation. This may cause an isochronous channel or bandwidth allocation to be retained or reallocated after the client is closed, resulting in resource leakage and reduced FireWire availability. For the CVSS the PR:L value is used because a local process must have permission to access the FireWire character device and create the affected client resource. AC:H is used because successful triggering depends on a timing window between the asynchronous work item and file descriptor release. The issue is not network reachable and requires a local FireWire device and the relevant kernel subsystem. The demonstrated impact is resource retention and denial of service, with no supported UAF, OOB access, information disclosure, or privilege escalation primitive. Automated impact decision path. The original SimpleNet classifier selected MODERATE. The primary LLM estimated paranoid CVSS 4.7 and the production ActionableScore returned 1 with recommendation Ordinary Moderate. The production rules then evaluated CVSS thresholds and ActionableScore thresholds. Recorded rule transitions were CVSS and initial triage stage MODERATE to LOW because the CVSS score, vector or bug class threshold 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_LOW_FROM_MODERATE_BASED_ON_GUESSCVSS_AND_CIANNH. The independent weaker Aegis shadow evaluated CVSS 2.6 and ActionableScore 0 with primitive class CLASS_C and manual review RECOMMENDED. Its independently reconciled impact was LOW. The shadow agreed with the final production impact and aggregation did not change that impact. The final reported impact is LOW.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 1)	MAYBE	SIMPLEFIX LINUS  DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_GUESSCVSS_AND_CIANNH	-	-	checked

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

ActionableScore=1
PrimitiveClass=CLASS_C
RealUAF=NO
HostAdminRequired=UNKNOWN
NamespaceScopedPrivilege=UNKNOWN
ImportantCandidate=NO
ManualReview=NO
AutoDowngradeAllowed=YES
RequiresHostUID0=UNKNOWN
AuthorizationDecisionBypass=NO
ProtectedResourceImpact=NONE
B4PendingReview=NO
B4PendingConfirmed=NO

1. ActionableScore

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

2. Signal breakdown

* +1 Concrete resource lifecycle defect. The work item can overwrite ISO_RES_AUTO_DEALLOC with ISO_RES_AUTO_REALLOC, potentially retaining or reallocating an isochronous channel or bandwidth resource after client release.
* No additional availability point. Host-wide exhaustion, persistent system failure, or a reliable kernel crash is not established.
* No race penalty. Concurrent work and file release are established, but the evidence does not show that the timing window is narrow, one-shot, or difficult to repeat.
* No privilege penalty. Access requirements for the FireWire character device are not supplied, so host-admin access cannot be assumed.
* No hardware rarity penalty. A FireWire device is a prerequisite, but the supplied evidence does not establish a sufficiently rare and difficult-to-reach configuration for a numeric reduction.
* No UAF, OOB access, repeated release, refcount corruption, controlled overwrite, authorization bypass, or cross-boundary primitive is established.
* V33 does not apply. Although todo is active state, no privileged downstream consumer or credible guest, namespace, or delegated-interface security boundary is identified.
* B5-R does not apply because no heap OOB write or retry-accumulated offset exists.
* B3-PENDING does not apply because no shared-backing write exists.
* B4-PENDING does not apply because no authorization decision changes from DENY to ALLOW.

3. Reachability analysis

A process must first obtain an open FireWire cdev file descriptor, create or use an automatic isochronous resource, and race its asynchronous work item against file descriptor release. Device-node permissions and the need for host-administrator powers are not shown, so HostAdminRequired and RequiresHostUID0 remain UNKNOWN. No evidence establishes that namespace-scoped capabilities provide the complete trigger, and no network-reachable path exists.

A FireWire controller and relevant device setup are practical prerequisites. The actor can influence the release side by closing the descriptor, but the supplied code does not establish precise control over workqueue scheduling or reliable repetition of the race.

4. Primitive and severity interpretation

The exact primitive is an invalid backward transition in an active resource state machine. The release path can set todo to ISO_RES_AUTO_DEALLOC, after which iso_resource_auto_work can incorrectly replace it with ISO_RES_AUTO_REALLOC.

This is CLASS_C invalid-state and resource-lifecycle behavior. It is not a post-lifetime object access. There is no evidence that the resource object is freed before the work item accesses it, and there is no second free, put, or refcount mutation through a dangling reference. The demonstrated mechanism can lose a deallocation request and retain or reallocate an isochronous resource, but it does not establish kernel memory corruption, a crash, disclosure, privilege escalation, or a security-boundary bypass.

ImportantCandidate is NO because the active-state corruption remains confined to FireWire resource management and no privileged cross-boundary consumer or useful corruption primitive is identified. AutoDowngradeAllowed is YES because the supported impact is a constrained resource-management defect without unresolved Important-grade leverage.

5. One-sentence report phrase

A race between FireWire isochronous resource work and file descriptor release can reverse a pending deallocation into reallocation, potentially retaining channel or bandwidth resources without establishing memory corruption or privilege escalation.

6. Manual review recommendation

NO MANUAL CHECK NEEDED

The patch supports a constrained state-machine and resource-retention defect, while no UAF, OOB write, authorization bypass, host-wide crash, or credible cross-boundary corruption chain is established.

7. Call-site confidence

Call-site confidence: medium

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

Patch: firewire: cdev: fix back-transition for iso_resource_auto client resource [ Upstream
Commit: ee1df60a0d0e8ab4b00137135733bdadd6d33dab
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=ee1df60a0d0e8ab4b00137135733bdadd6d33dab

Changed files:
  drivers/firewire/core-cdev.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=ee1df60a0d0e8ab4b00137135733bdadd6d33dab

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

The original Linux kernel CVE announcement for CVE-2026-98587 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98587

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:N/I:N/A:L
  The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS score: 4.7

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: 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).