[CVE-2026-45860][MODERATE 7.0] netfilter: nf_conncount: increase the connection clean up limit to 64 [ Upstream

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

CVE: CVE-2026-45860
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: netfilter: nf_conncount: increase the connection clean up limit to 64 [ Upstream
Commit: a5c9e14e0e8923218ae881d5e78c990c07694966
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=a5c9e14e0e8923218ae881d5e78c990c07694966
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-45860
Analysis date: Thu, 28 May 2026 00:23:19 -0400
ActionableScore: 5
ActionableScore lower bound: 4
Actionable bucket: Actionable Moderate at minimum
Manual review required: NO

Summary:
nf_conncount could skip garbage collection too aggressively and keep stale connection entries counted, allowing remote connection churn against configured connlimit policies to cause incorrect limit hits and denial of new legitimate connections.

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

The original Linux kernel CVE announcement for CVE-2026-45860 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-45860

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: NO

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-2026-45860	MODERATE	CHECK	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H';**CWE-400;CWE-404;CWE-703;Other CVSS 'AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '5.9';DESCR 'nf_conncount could skip garbage collection too aggressively after the one GC per jiffy optimization, leaving stale connection entries counted for too long. A remote client can contribute to the condition by creating connections faster than the cleanup path can retire old entries when nft_connlimit, xt_connlimit, or OVS connection limits are configured. For the CVSS the PR:N is used because the paranoid network scenario only requires the ability to open connections to the protected service, not local access on the target. The issue is network reachable only in deployments that use connlimit policy and the realistic impact is denial of service through incorrect rejection of new connections, not kernel memory corruption or privilege escalation.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 5) 	MAYBE	REMOTE NETFILTER LINUS TEST  KPANIC INCREASED_TO_MODERATE70_BASED_ON_ACTIONABLESCOREHIGHEREQTHAN5	-	-	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=5
ActionableScoreLower=4

## 1. ActionableScore

* Conservative score: 4
* Paranoid score: 5
* Final recommended bucket: **Actionable Moderate at minimum**::

## 2. Signal breakdown

Conservative signals:

* Remote reachable / network-triggerable: +2. A remote client can contribute by opening many connections to a service protected by nft_connlimit, xt_connlimit, or OVS connection limits.
* Reliable service DoS: +1. Stale conncount entries may cause the configured limit to be reached incorrectly, rejecting legitimate new connections.
* Availability impact realistic: +1. The impact is service availability degradation or denial for new connections.

Paranoid additional signal:

* Common networking / netfilter path: +1. This is in netfilter connection counting used by firewall and OVS connection limiting policies, so network-facing deployments deserve manual triage.

Not counted:

* No generic memory corruption. The patch changes GC pacing and accounting, not object lifetime safety.
* No privilege escalation primitive.
* No confidentiality or integrity impact.
* No local privilege requirement for the network scenario, but the vulnerable policy must be configured by an administrator.

## 3. Reachability analysis

The bug is reachable by remote traffic only when connlimit functionality is deployed through nft_connlimit, xt_connlimit, or OVS limit configuration. An attacker does not need local code execution on the target in that scenario, only the ability to create connections to the protected service at a sufficient rate.

Namespaces and containers mainly matter for who can configure connlimit rules, but exploitation of an already configured rule can be remote. The feature is not universally default-enabled, but netfilter and connection limiting are common enough in firewall, gateway, and service protection deployments that this should not be treated as a purely obscure configuration issue.

## 4. Severity interpretation

This behaves like an actionable Moderate issue, not an Important memory-corruption vulnerability. The realistic impact is incorrect connection limiting and denial of new legitimate connections under high connection churn. There is no evidence of UAF, OOB access, arbitrary write, information disclosure, or privilege escalation.

The paranoid score reaches 5 because the issue can be network-triggered in configured deployments and can affect externally visible service availability.

## 5. One-sentence report phrase

nf_conncount could skip garbage collection too aggressively and keep stale connection entries counted, allowing remote connection churn against configured connlimit policies to cause incorrect limit hits and denial of new legitimate connections.

## 6. Manual review recommendation

MANUAL CHECK RECOMMENDED

Network reachability makes this worth manual triage for exposed firewalls, gateways, OVS deployments, or public services using connlimit, but the supported impact is availability only and there is no memory corruption or privilege escalation evidence.

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

Patch: netfilter: nf_conncount: increase the connection clean up limit to 64 [ Upstream
Commit: a5c9e14e0e8923218ae881d5e78c990c07694966
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=a5c9e14e0e8923218ae881d5e78c990c07694966

Changed files:
  include/net/netfilter/nf_conntrack_count.h
  net/netfilter/nf_conncount.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=a5c9e14e0e8923218ae881d5e78c990c07694966

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

The original Linux kernel CVE announcement for CVE-2026-45860 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-45860

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:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L
  The Best / paranoid CVSS vector: AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS score: 5.9

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).