[CVE-2026-72430][LOW] net/sched: act_ct: fix nf_connlabels leak on two error paths [ Upstream

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

CVE: CVE-2026-72430
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: net/sched: act_ct: fix nf_connlabels leak on two error paths [ Upstream
Commit: 13b561c893c741635adce3781490a7a1099106c8
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=13b561c893c741635adce3781490a7a1099106c8
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72430
Analysis date: Sun, 16 Aug 2026 04:31:51 -0400
ActionableScore: 2
ActionableScore lower bound: unknown
Actionable bucket: Ordinary Moderate / Low-like
Manual review required: NO

Summary:
No one-sentence report phrase was found.

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

The original Linux kernel CVE announcement for CVE-2026-72430 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72430

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-2026-72430	LOW	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-772;CWE-404;**CWE-400;Other CVSS 'AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '5.5';DESCR 'act_ct can leak nf_connlabels references when tcf_ct_fill_params handles TCA_CT_LABELS and then exits through two later error paths without running the common cleanup path. A local attacker can repeat failed RTM_NEWACTION requests to keep net ct labels_used elevated and retain connlabels state beyond its intended lifetime. For the CVSS the PR:L is used because triggering requires CAP_NET_ADMIN over a network namespace, and on default userns kernels this can be reachable by an unprivileged local user inside a created netns. The issue is not directly network reachable and it is triggered through local traffic control configuration rather than packet traffic. Impact is resource exhaustion or local denial of service only, with no supported UAF, OOB write, information leak, or privilege escalation primitive in the patch context.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like (with actual score 2)	YES	REMOTE NOMEMCHK SIMPLEFIX LEAK ERRORPATH NETWORK LINUS  LOWERED_FROM_HIGH_BASED_ON_GUESSCVSS  DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5 DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3	YES	NO	checked

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

ActionableScore=2

1. ActionableScore
* Conservative score: 2
* Paranoid score: 2
* Final recommended bucket: **Ordinary Moderate / Low-like**

2. Signal breakdown
* Local unprivileged trigger: +1. The action requires CAP_NET_ADMIN over a network namespace, but on systems with unprivileged user namespaces enabled this can be reachable by a local unprivileged user inside a created netns.
* Availability impact realistic: +1. Repeated failed RTM_NEWACTION requests can leak nf_connlabels references and keep net->ct.labels_used elevated, creating a resource leak / local DoS concern.
* Remote reachable / network-triggerable: +0. This is a local tc/netlink control-plane path, not packet-triggered remotely.
* Privilege escalation plausible: +0. The patch shows a reference leak, not UAF, OOB write, object replacement, callback control, or arbitrary write.
* Generic memory corruption: +0. No memory corruption primitive is supported by the patch.
* Reliable kernel crash / strong DoS: +0. Sustained resource leakage is plausible, but the patch does not show an immediate reliable crash or panic.
* Requires admin/root/CAP_NET_ADMIN in typical deployments: not applied as -2 for the main score because namespace delegation can make this reachable from an unprivileged local user on default-userns systems. If unprivileged user namespaces are disabled, the practical score would be lower.

Call-site confidence: high. The changed error paths and skipped cleanup are directly visible in the supplied patch and commit message.

3. Reachability analysis
A local process that can issue tc RTM_NEWACTION operations with act_ct parameters can trigger the leak. In a host-only model this normally requires CAP_NET_ADMIN, but with unprivileged user namespaces enabled a local user may obtain CAP_NET_ADMIN inside a created network namespace. The path is not remotely reachable through packet traffic. Exploitation requires repeated failed action creation on the specific error paths after nf_connlabels_get() succeeds.

4. Severity interpretation
This behaves like an ordinary Moderate / Low-like resource leak. The realistic impact is local resource exhaustion or persistent connlabels reference leakage inside the affected net namespace. There is no supported evidence of UAF, OOB access, arbitrary write, information disclosure, or privilege escalation.

5. One-sentence report phrase
A local user with CAP_NET_ADMIN over a network namespace can repeatedly trigger failed act_ct RTM_NEWACTION paths that leak nf_connlabels references, causing a resource leak and possible local denial of service without evidence of memory corruption or privilege escalation.

6. Manual review recommendation
NO MANUAL CHECK NEEDED.
This is a local reference leak / resource exhaustion issue with namespace-dependent reachability and no concrete memory corruption or privilege-escalation primitive.

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

Patch: net/sched: act_ct: fix nf_connlabels leak on two error paths [ Upstream
Commit: 13b561c893c741635adce3781490a7a1099106c8
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=13b561c893c741635adce3781490a7a1099106c8

Changed files:
  net/sched/act_ct.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=13b561c893c741635adce3781490a7a1099106c8

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

The original Linux kernel CVE announcement for CVE-2026-72430 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72430

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