* [CVE-2026-97616][LOW] net/sched: act_api: release all action references on NEWACTION failure
@ 2026-09-25 11:59 21% AL-KERNEL
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From: AL-KERNEL @ 2026-09-25 11:59 UTC (permalink / raw)
To: kernel-cve
CVE: CVE-2026-97616
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: net/sched: act_api: release all action references on NEWACTION failure
Commit: f908c8a969946a45225fd7f9d9a85771e12ae0a8
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=f908c8a969946a45225fd7f9d9a85771e12ae0a8
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-97616
Analysis date: Fri, 25 Sep 2026 07:59:46 -0400
ActionableScore: 2
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-2026-97616 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-97616
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-2026-97616 LOW https://www.kernelcve.org/list/?q=CVE-2026-97616 CHECK WITH IMPACT FROM ORIG NN IMPORTANT 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-401;*CWE-772;**CWE-400;Other CVSS 'AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '5.5';DESCR 'A failed batched RTM_NEWACTION request can leak traffic control action references and reserved IDR indices when cleanup encounters an action that is still bound to a filter. Repeated local control plane requests can accumulate unreleased actions and index slots, potentially causing resource exhaustion or preventing later action index reuse. For the CVSS the PR:L paranoid score assumes an attacker has delegated CAP_NET_ADMIN, a service account, or container level network administration rights rather than full host administration. The issue is not directly network reachable because packet traffic alone does not invoke the affected cleanup path. Impact is denial of service through resource exhaustion. No memory corruption primitive, information disclosure, integrity impact, or privilege escalation path is indicated by the patch context.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 2) YES 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 NO NO checked
======================================================================
ACTIONABLESCORE ANALYSIS
======================================================================
ActionableScore=2
PrimitiveClass=NONE
RealUAF=NO
HostAdminRequired=UNKNOWN
NamespaceScopedPrivilege=UNKNOWN
ImportantCandidate=NO
ManualReview=NO
AutoDowngradeAllowed=YES
1. ActionableScore
* Raw conservative score: 2
* Conservative score: 2
* Raw paranoid score: 2
* Paranoid score: 2
* Final recommended bucket: **Ordinary Moderate**::
2. Signal breakdown
* +1 Concrete persistent kernel resource and reference leak. A temporary action reference acquired during batched RTM_NEWACTION processing is not dropped when strict cleanup encounters an action bound to a filter.
* +1 Repeatable resource exhaustion effect. The cleanup returns early and leaves subsequent initialized actions and their reserved IDR slots unreleased. Repeated malformed or failing batches can accumulate unreusable action indices and references.
* +0 No UAF or repeated lifetime mutation. The defective path fails to drop a reference. It does not release an object and later release the same dangling reference.
* +0 Controlled reclaim, arbitrary write, callback control, disclosure, integrity impact, and privilege escalation are not demonstrated.
* +0 Remote reachability is not established. The vulnerable path is reached through local rtnetlink RTM_NEWACTION control-plane requests, not normal packet processing.
* +0 No host-admin penalty was applied. CAP_NET_ADMIN is relevant to traffic-control operations, but the supplied patch does not establish whether the complete trigger requires initial user namespace authority or can be completed in an attacker-controlled network namespace.
* +0 No rare-subsystem penalty was applied. Traffic-control actions are runtime-configurable objects, and the patch does not establish an unusual hardware or boot-time prerequisite.
3. Reachability analysis
The trigger requires creating or replacing traffic-control actions through batched RTM_NEWACTION requests and arranging a later action initialization failure after an existing action bound to a filter is encountered.
Traffic-control netlink operations normally require CAP_NET_ADMIN, commonly checked relative to the target network namespace. However, the supplied patch does not show the complete capability checks, whether all required action and filter setup operations are namespace-scoped, or whether an unprivileged attacker can create the required user and network namespace configuration in the evaluated product.
Therefore, host-admin-equivalent privilege is not positively established, but below-host-admin reachability is also not fully established. HostAdminRequired and NamespaceScopedPrivilege remain UNKNOWN. No special hardware, firmware, race condition, boot option, or privileged prior host setup is identified by the patch.
4. Primitive and severity interpretation
The established defect is a cleanup logic failure and persistent resource leak. `tcf_idr_check_alloc()` obtains a temporary reference while processing a batch. On a later initialization failure, the old strict cleanup helper rejects an action still bound to a filter with `-EPERM`, does not drop the temporary reference, and stops cleanup before subsequent actions and IDR reservations are released.
This is not an ordinary stale cleanup dereference and not a repeated release or refcount UAF. The first relevant operation does not destroy the object. Instead, the error path omits the required reference release. No dangling reference is shown to undergo a later put, release, free, or refcount mutation.
PrimitiveClass is NONE because no kernel memory corruption, lifetime violation, authorization bypass, or attacker-useful ownership primitive is established. The demonstrated impact is accumulated resource leakage and possible denial of service through exhaustion of action objects or reserved IDR indices. The scope may be limited to the affected network namespace, but that cannot be confirmed from the supplied context.
ImportantCandidate is NO because this is a resource-management leak without a demonstrated corruption, boundary-bypass, cross-namespace exhaustion, or privilege-escalation primitive. AutoDowngradeAllowed is YES because automatic closure would not discard a concrete unresolved memory-corruption or security-boundary primitive.
5. One-sentence report phrase
A failed batched RTM_NEWACTION request can leak traffic-control action references and reserved IDR indices, allowing repeated local control-plane requests to cause resource exhaustion or prevent action index reuse.
6. Manual review recommendation
NO MANUAL CHECK NEEDED
The patch establishes a reference and IDR-slot leak only. No UAF, double release, stale-object access, arbitrary write, information disclosure, authorization bypass, or privilege-escalation path is shown.
7. Call-site confidence
Call-site confidence: medium
======================================================================
UPSTREAM PATCH SUMMARY
======================================================================
Patch: net/sched: act_api: release all action references on NEWACTION failure
Commit: f908c8a969946a45225fd7f9d9a85771e12ae0a8
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=f908c8a969946a45225fd7f9d9a85771e12ae0a8
Commit description:
When a batched RTM_NEWACTION request replaces an existing action,
tcf_idr_check_alloc() takes a temporary reference on it. If a later
action fails to initialize, tcf_action_destroy() uses strict release
semantics to clean up the actions initialized so far. For an action
bound to a filter, the strict check returns -EPERM without dropping
the temporary reference.
This error also makes tcf_action_destroy() return before releasing
subsequent entries. Any new action initialized between the bound
action and the failing entry is leaked together with its reserved
IDR slot, preventing reuse of its index.
Use tcf_idr_release() to drop each reference held by the batch without
rejecting bound actions. This allows cleanup to continue through all
initialized entries and preserves the module reference release when
an action is destroyed. Explicit action deletion and flushing retain
their separate bind-count checks.
Fixes: 55334a5 ("net_sched: act: refuse to remove bound action outside")
Cc: [email protected]
Signed-off-by: Xuanqiang Luo <[email protected]>
Reviewed-by: Jamal Hadi Salim <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Jakub Kicinski <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
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=f908c8a969946a45225fd7f9d9a85771e12ae0a8
======================================================================
DETAILED REPORT METHODOLOGY
======================================================================
The original Linux kernel CVE announcement for CVE-2026-97616 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-97616
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:H/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: 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: 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 [email protected] (and both
send reply to CVE record itself too and see "reply" button below for howto reply).
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