[CVE-2026-98235][LOW] net/sched: act_api: release tail references on DELACTION failure

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

CVE: CVE-2026-98235
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: net/sched: act_api: release tail references on DELACTION failure
Commit: 9eaba16f1b6ee19b249e6afd82c27f958d441458
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=9eaba16f1b6ee19b249e6afd82c27f958d441458
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98235
Analysis date: Fri, 09 Oct 2026 12:01:42 -0400
ActionableScore: 1
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-2026-98235 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98235

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-2026-98235	LOW	https://www.kernelcve.org/list/?q=CVE-2026-98235 CHECK WITH IMPACT FROM ORIG NN IMPORTANT | AEGIS IMPACT LOW AEGIS_AS=1 LEGACY=LOW RESULT=SAME (legacy and Aegis reconciliation agree; DECISION: both LOW)	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H';*CWE-772;CWE-911;*CWE-401;Other CVSS 'AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '5.5';DESCR 'A failed batched RTM_DELACTION request can leak temporary references to actions that follow the first cleared array slot. The iterator in tcf_action_put_many stops at that NULL slot and does not release references held on later actions. Repeated failures may retain action objects in the IDR and consume kernel resources, while a later deletion can report success without actually removing an action. For the CVSS the PR:L value is used because reliable triggering requires access to the tc control plane, normally through CAP_NET_ADMIN, but this capability can be delegated to a restricted container or network namespace user. The issue is local and is not triggered directly by network packets. The demonstrated impact is limited resource retention with A:L, while the paranoid A:H case assumes repeatable accumulation sufficient to cause resource exhaustion. No UAF, out of bounds access, information disclosure, or memory write primitive is established by the affected path.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 1)	MAYBE	REMOTE SIMPLEFIX LEAK NETWORK LINUS  LOWERED_FROM_HIGH_BASED_ON_GUESSCVSS  DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN4 DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3	-	-	checked

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

ActionableScore=1
PrimitiveClass=CLASS_C
RealUAF=NO
HostAdminRequired=UNKNOWN
NamespaceScopedPrivilege=UNKNOWN
ImportantCandidate=NO
ManualReview=NO
AutoDowngradeAllowed=YES

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

Positive signals:

* +1 Concrete persistent kernel resource/reference leak. Temporary references acquired for unprocessed actions are not released after deletion stops at a bound action.
* +0 Resource exhaustion. Repetition can retain additional actions, but practical host-wide exhaustion from a constrained workload is not established.
* +0 Invalid IDR state. A later deletion may report success without removing the action, but this is bookkeeping inconsistency rather than demonstrated unauthorized integrity impact.

Negative signals:

* No negative points. Host-admin privilege, difficult timing, rare configuration, and special hardware are not established.

Important non-awarded signals:

* No heap or slab OOB write is present.
* B5-R does not apply. There is no retry-accumulated index, OOB write, or later consumption of OOB-corrupted structured state.
* No UAF, dangling dereference, double release, or post-lifetime refcount mutation is established.
* No controlled reclaim, arbitrary write, disclosure, authorization bypass, or privilege escalation is demonstrated.
* No crash or host-wide resource exhaustion is established, so no reliable DoS point is awarded.
* No C or I impact is awarded for the stale IDR entry alone.
* The paranoid score receives no additional point because repeatable leakage does not independently establish broad exhaustion or an isolation-boundary bypass.

Repeated-release checks:

* The processed actions have their temporary references dropped normally.
* The defect is failure to release references on later, unprocessed actions.
* The same reference is not released once and then released again after becoming dangling.
* Concrete repeated release/refcount +1 does not apply.
* Paranoid repeated-refcount leverage +1 does not apply.
* REAL UAF FLOOR 5 does not apply.

3. Reachability analysis

The trigger is a local batched RTM_DELACTION control-plane request containing an action whose deletion fails because it remains bound to a filter, followed by additional actions whose temporary references are leaked.

Traffic-control action management normally requires CAP_NET_ADMIN. The supplied patch does not show the applicable capability check or prove whether every required stage, including action creation, filter binding, batch deletion, and repetition, can be completed in an attacker-created user and network namespace. Therefore HostAdminRequired and NamespaceScopedPrivilege remain UNKNOWN.

There is no direct packet-triggered or remote path. No race, special timing, boot option, hardware requirement, or retry-sensitive memory operation is involved. Repeating the control-plane sequence appears possible for an actor with the necessary tc permissions, but the evidence does not establish efficient host-wide exhaustion.

4. Primitive and severity interpretation

The exact primitive is a missing reference release during cleanup of a partially processed action array. The old iterator treats the first NULL slot as the end of the array, even though later slots still hold temporary references.

This is not stale storage or an active-object UAF. The leaked references preserve object lifetime rather than ending it prematurely. There is no second lifetime mutation through a dangling object.

PrimitiveClass is CLASS_C because the demonstrated effects are resource retention and inconsistent deletion state without an independently useful memory-corruption, ownership, or authorization primitive. The practical consequence is a persistent action-reference leak and possible gradual resource consumption. Host-wide DoS remains a plausible operational concern under sustained abuse but is not demonstrated strongly enough for another point.

ImportantCandidate is NO because the B5-R preservation requirements are not met and no Important-grade primitive exists. AutoDowngradeAllowed is YES because no unresolved corruption or security-boundary primitive would be lost by treating this as an ordinary resource-management issue.

5. One-sentence report phrase

A failed batched RTM_DELACTION can leak temporary references to later actions and leave them retained in the IDR, but the patch establishes only a local resource leak and inconsistent deletion state rather than memory corruption or privilege escalation.

6. Manual review recommendation

NO MANUAL CHECK NEEDED

The defect is a concrete reference leak, but it has no UAF, OOB write, authorization bypass, demonstrated host-wide exhaustion, or other Important-preserving primitive.

7. Call-site confidence

Call-site confidence: medium

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

Patch: net/sched: act_api: release tail references on DELACTION failure
Commit: 9eaba16f1b6ee19b249e6afd82c27f958d441458
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=9eaba16f1b6ee19b249e6afd82c27f958d441458

Commit description:

A batched RTM_DELACTION request takes a temporary reference on each
action before attempting any deletion. tcf_action_delete() clears
each processed slot and drops its temporary reference before attempting
the deletion. If deletion fails, tca_action_gd() calls
tcf_action_put_many() to release the remaining references, but its
tcf_act_for_each_action() iterator stops at the first NULL slot.

When a batch stops at an action bound to a filter, this leaks a
reference on each subsequent action. A later delete of an unbound
action can then return success without removing it from the IDR.

Walk the full array in tcf_action_put_many() and skip NULL slots to
release the references held on the unprocessed actions.

Fixes: a0e947c ("net/sched: act_api: avoid non-contiguous action array")
Cc: stable@vger.kernel.org
Signed-off-by: Xuanqiang Luo <luoxuanqiang@kylinos.cn>
Link: https://patch.msgid.link/20260910093413.34509-2-xuanqiang.luo@linux.dev
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  net/sched/act_api.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=9eaba16f1b6ee19b249e6afd82c27f958d441458

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

The original Linux kernel CVE announcement for CVE-2026-98235 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98235

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:L/PR:L/UI:N/S:U/C:N/I:N/A:L
  The Best / paranoid CVSS vector: AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS score: 5.5

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).