[CVE-2026-98709][MODERATE 7.0] wifi: mac80211: count only matching reservations in reserved switch [ Upstream

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

CVE: CVE-2026-98709
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: wifi: mac80211: count only matching reservations in reserved switch [ Upstream
Commit: d31f655e44631891788ca67018ec5e1ed1c7de86
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=d31f655e44631891788ca67018ec5e1ed1c7de86
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98709
Analysis date: Mon, 19 Oct 2026 01:31:18 -0400
ActionableScore: 5
ActionableScore lower bound: 4
Actionable bucket: Actionable Moderate / Strong Important candidate requiring manual review
Manual review required: YES

Summary:
Incorrect matching of mac80211 channel reservations can free an active channel context while a link and driver still reference it, causing a use-after-free during later beacon generation and requiring manual review for exploitation potential beyond kernel denial of service.

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ABOUT THIS REPORT
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The original Linux kernel CVE announcement for CVE-2026-98709 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98709

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 7.0
Manual review required: YES

A detailed explanation of the methodology and priority rules is included
at the end of this message.

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AL-KERNEL CLASSIFICATION RESULT
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CVE-2026-98709	MODERATE	https://www.kernelcve.org/list/?q=CVE-2026-98709 CHECK WITH IMPACT FROM ORIG NN IMPORTANT | AEGIS IMPACT MODERATE_KPANIC AEGIS_AS=4 LEGACY=MODERATE_KPANIC RESULT=SAME (final reconciliation agrees; DECISION: both 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-670;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:L/I:L/A:H';BEST CVSS score: '7';DESCR 'A channel context replacement can be considered complete too early because ieee80211_vif_use_reserved_switch counts reservations that belong to a different replacement operation. Another link can then finalize first and free a WILL_BE_REPLACED channel context while an unmatched link and the driver still reference it. Later beacon generation can dereference the freed object, resulting in a confirmed use-after-free and at least a kernel crash or denial of service. For the CVSS the PR:L value is used for the paranoid score because delegated CAP_NET_ADMIN, a restricted network service account, or a container administrator may control wireless configuration without having unrestricted host privileges. Reliable triggering requires a multi-link or multi-vif configuration, overlapping replacement state, and a specific completion order, so AC:H is appropriate. The issue is not proven to be directly reachable through untrusted WiFi traffic alone and AV:L is retained. In the worst defensible case the freed object could be reused and produce confidentiality or integrity impact or local privilege escalation, although a controlled reuse primitive is not established by the available code. Automated impact decision path. The original SimpleNet classifier selected IMPORTANT. The primary LLM estimated paranoid CVSS 7 and the production ActionableScore returned 5 with recommendation Actionable Moderate / Strong Important candidate requiring manual review. The production rules then evaluated CVSS thresholds and ActionableScore thresholds. Recorded rule transitions were KP and FD specialist checks stage IMPORTANT to MODERATE_KPANIC because FD false positive review allowed a downgrade. The legacy KP specialist produced a review artifact and its decision was processed by the applicable KP rules. The legacy FD or DH downgrade specialist produced a review artifact and its decision was processed by the applicable downgrade and preservation rules. Exact triggered rule markers were DECREASED_TO_MODERATE7_BASED_ON_FALSEPOSCHECKOFDH. The independent weaker Aegis shadow evaluated CVSS 4.1 and ActionableScore 4 with primitive class CLASS_B and manual review REQUIRED. Its independently reconciled impact was MODERATE_KPANIC. The shadow agreed with the final production impact and aggregation did not change that impact. The final reported impact is MODERATE_KPANIC.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate / Strong Important candidate requiring manual review (with actual score 5)	MAYBE	REMOTE DANGER UAF KPANIC  DECREASED_TO_MODERATE7_BASED_ON_FALSEPOSCHECKOFDH	-	-	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=5
ActionableScoreLower=4
PrimitiveClass=CLASS_B
RealUAF=YES
HostAdminRequired=UNKNOWN
NamespaceScopedPrivilege=UNKNOWN
ImportantCandidate=YES
ManualReview=REQUIRED
AutoDowngradeAllowed=NO
RequiresHostUID0=UNKNOWN
AuthorizationDecisionBypass=NO
ProtectedResourceImpact=NONE
B4PendingReview=NO
B4PendingConfirmed=NO

1. ActionableScore

* Raw conservative score: 3
* Conservative score: 4
* Raw paranoid score: 5
* Paranoid score: 5
* Applied conservative floor: 3 -> 4 under REAL UAF FLOOR 4. The stale active object is used after free outside a narrow cleanup-only path, and host-admin-equivalent privilege is not positively established.
* No paranoid floor or cap was applied.
* Final recommended bucket: **Actionable Moderate / Strong Important candidate requiring manual review**::

2. Signal breakdown

Conservative signals:

* +2 Real UAF. The old WILL_BE_REPLACED channel context can be freed while an unmatched link and the driver retain references to it.
* +1 Realistic kernel crash or strong DoS. Later beacon generation dereferences the freed channel context, making an Oops or kernel crash technically credible.
* +0 privilege penalty. Host-admin-equivalent privilege is not positively established, so no speculative -2 penalty is applied.
* +0 race penalty. A specific ordering between replacement completions is required, but the evidence does not establish a narrow, one-shot, or externally uncontrollable timing window.

Paranoid additional signals:

* +1 Attacker-influenced active-object lifetime manipulation. Under the technically defensible local control-plane model, an actor able to initiate overlapping multi-vif or multi-link channel replacements can repeatedly influence the transition that frees the context.
* +1 Structured stale-object leverage. The dangling chanctx is not merely passed to cleanup. It remains associated with an active link and driver and is later consumed during beacon generation. This is distinct from the lifetime-transition point above.

Important non-awarded signals:

* Controlled reclaim, attacker-shaped replacement contents, arbitrary kernel read or write, callback control, and privilege escalation are not demonstrated.
* No confidentiality or integrity point is awarded solely because heap reuse after the UAF is theoretically possible.
* No extra availability point is awarded because it would duplicate the same potential kernel crash.
* No concrete repeated release or refcount operation on the exact dangling reference is shown. The dedicated repeated-release +1 and its paranoid variant are therefore withheld.
* FLOOR 5 is not applied to the conservative score because below-host-admin reachability and attacker control of the complete replacement sequence are unresolved.
* Direct remote or adjacent-network triggering by untrusted WiFi traffic is not established.
* B5-R does not apply because there is no retry-accumulated heap OOB write.
* B3-PENDING does not apply because no shared-backing write is involved.
* B4-PENDING does not apply because no authorization DENY-to-ALLOW decision is changed.
* V33 is not independently established because no concrete namespace, guest, or delegated-interface trust-boundary crossing is demonstrated.

3. Reachability analysis

The vulnerable state arises during overlapping mac80211 channel-context replacement operations involving multiple links or virtual interfaces. The likely trigger is a local wireless control-plane or driver operation rather than ordinary packet reception.

The supplied patch does not establish whether the complete operation requires host-owned CAP_NET_ADMIN, can be performed by a delegated wireless-management service, or works entirely within an attacker-created user or network namespace. Therefore both HostAdminRequired and NamespaceScopedPrivilege remain UNKNOWN. Numeric UID 0 is not shown as an explicit prerequisite.

A configured mac80211 device and a multi-vif or multi-link replacement sequence are prerequisites. This is hardware-dependent but not proven to require rare physical hardware, so no hardware penalty is applied. The required completion order supports complexity in CVSS terms, but there is insufficient evidence that the ordering is too narrow or unreliable for ActionableScore subtraction.

External CSA or other WiFi management traffic might influence channel switching in some modes, but the supplied call path does not establish that an unauthenticated station can perform the complete vulnerable sequence. Remote or adjacent reachability is therefore not scored.

4. Primitive and severity interpretation

The exact primitive is an active structured-object UAF. Incorrect reservation matching causes the replacement operation to appear complete and permits the old chanctx to be freed while an unmatched link and the driver still use it. Beacon generation later consumes the stale object.

This is broader than an ordinary cleanup or destructor dereference because the stale context remains part of active wireless processing. It is not a concrete double release or second refcount mutation. The first free ends the chanctx lifetime, but no second free, put, or refcount operation on the same reference is shown.

PrimitiveClass is CLASS_B because a real active-object lifetime violation exists, but controlled reclaim or another CLASS_A exploitation primitive is absent. The demonstrated consequence is use-after-free with credible kernel DoS. Reuse-based corruption, information disclosure, and local privilege escalation remain unresolved possibilities rather than established consequences.

ImportantCandidate is YES because an active chanctx survives into driver and beacon processing, leaving meaningful exploitation leverage unresolved. AutoDowngradeAllowed is NO because automatically treating this as an ordinary crash-only issue would discard the confirmed active-object UAF and its nontrivial downstream use. This does not prove Important severity.

5. One-sentence report phrase

Incorrect matching of mac80211 channel reservations can free an active channel context while a link and driver still reference it, causing a use-after-free during later beacon generation and requiring manual review for exploitation potential beyond kernel denial of service.

6. Manual review recommendation

MANUAL CHECK REQUIRED

Review the chanctx allocator and free path, stale fields consumed during beacon generation, driver callbacks, reclaim opportunities, nl80211 privilege checks, namespace scope, and whether external channel-switch events can induce the complete sequence below host-admin privilege.

7. Call-site confidence

Call-site confidence: medium

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UPSTREAM PATCH SUMMARY
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Patch: wifi: mac80211: count only matching reservations in reserved switch [ Upstream
Commit: d31f655e44631891788ca67018ec5e1ed1c7de86
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=d31f655e44631891788ca67018ec5e1ed1c7de86

Changed files:
  net/mac80211/chan.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=d31f655e44631891788ca67018ec5e1ed1c7de86

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

The original Linux kernel CVE announcement for CVE-2026-98709 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98709

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:H/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: 4
  Paranoid ActionableScore: 5

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: YES
Published priority for this report (same as in Subject): MODERATE 7.0

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).