[CVE-2026-80668][MODERATE 7.0] netfilter: nf_conntrack_expect: use conntrack GC to reap expectations [ Upstream

[CVE-2026-80668][MODERATE 7.0] netfilter: nf_conntrack_expect: use conntrack GC to reap expectations [ Upstream

[AL-KERNEL]

CVE: CVE-2026-80668
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: netfilter: nf_conntrack_expect: use conntrack GC to reap expectations [ Upstream
Commit: 7ec786f4230c2a9b2eaf97a2d45368933b49d2b2
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=7ec786f4230c2a9b2eaf97a2d45368933b49d2b2
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80668
Analysis date: Fri, 28 Aug 2026 07:03:23 -0400
ActionableScore: 5
ActionableScore lower bound: 4
Actionable bucket: Actionable Moderate at minimum
Manual review required: YES

Summary:
A race in netfilter conntrack expectation cleanup can leave an expectation with a stale exp master pointer after the master conntrack is released, creating a network influenced UAF candidate with at least kernel crash DoS impact and requiring manual review.

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

The original Linux kernel CVE announcement for CVE-2026-80668 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80668

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
======================================================================

CVE-2026-80668	MODERATE	CHECK WITH IMPACT FROM ORIG NN IMPORTANT	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H';*CWE-416;CWE-362;*CWE-664;Other CVSS 'AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '8.1';DESCR 'A race in netfilter conntrack expectation cleanup can allow an expectation timer path to access a stale exp master pointer after the master conntrack has already been released. This is a use-after-free candidate in kernel memory management rather than a pure warning or resource leak. A remote attacker may be able to influence expectation creation and expiration through packet paths on systems using conntrack helpers or expectation based NAT/firewall handling. For the CVSS the PR:N is used for the paranoid score because a network sender does not need a local account when the vulnerable packet path is reachable. AC:H is used because reliable triggering depends on winning a cleanup and expiration race. Impact is at least denial of service via kernel crash and in the worst case may allow confidentiality or integrity impact due to UAF style memory corruption. YES REQUIRES MANUAL CHECK';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 5)  SKIP CVE-2026-80668 UNKNOWN SKIP The Fixes patch not applied yet, so unlikely that actual: url YES  NO NO unknown 	MAYBE	REMOTE NETFILTER RACE ERRORPATH TIMER KPANIC PACKET  KPANIC DECREASED_TO_MODERATE70_BASED_ON_ACTIONABLESCORELOWERTHAN6	-	-	checked

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

ActionableScore=5
ActionableScoreLower=4

## 1. ActionableScore

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

## 2. Signal breakdown

* Remote reachable / network-triggerable: +2. Conntrack expectations can be created and expired through packet-path behavior when helpers or expectation-based firewall/NAT handling are enabled.
* Memory corruption, weak/indirect corruption candidate: +1. The commit explicitly mentions stale `exp->master` access after the master conntrack was released, which is a UAF candidate.
* Real lifetime corruption: +1. This is a timer/removal race involving object lifetime and stale pointer access.
* Reliable kernel crash / strong DoS: +1. A stale master conntrack pointer can plausibly lead to kernel crash or invalid memory access.
* Common networking core path or packet-processing path: +1. The affected code is in netfilter conntrack expectation handling.
* Hard or unreliable race / special timing required: -1. The problematic case depends on expectation removal racing with an expiring timer.
* Race-UAF downgrade cap applied. No attacker-controlled reclaim, write-after-free, callback dispatch, type confusion, or refcount takeover is shown in the supplied patch. Conservative score is capped at 4 and paranoid score at 5.

## 3. Reachability analysis

A remote sender may influence the vulnerable path only on systems where conntrack helpers or nftables expectation handling are configured and reachable by relevant traffic. This is not a generic TCP/IP bug affecting all hosts by default. It is more relevant for firewall, NAT, gateway, or service inspection deployments using conntrack expectations.

Local privileges are not required for the network packet-path interpretation, so PR:N is defensible for paranoid CVSS-style triage when the helper path is reachable. However, practical exposure depends heavily on runtime configuration, enabled helpers, and firewall policy. Namespaces may matter if an attacker can control netfilter configuration in a delegated network namespace, but the stronger concern here is remote packet influence on a configured firewall/NAT path.

Call-site confidence: medium. The provided diff shows GC integration and helper checks, and the commit message directly describes the stale `exp->master` lifetime race, but the full expectation removal and lookup call paths are not fully included.

## 4. Severity interpretation

This should not be treated as an ordinary Moderate that can be auto-closed. The realistic demonstrated impact is likely DoS from a race-dependent stale pointer access. The theoretical memory corruption concern is real because the patch context explicitly describes a released master conntrack pointer being accessed later.

At the same time, the patch does not show a strong exploitation primitive such as controlled reclaim, arbitrary write, type confusion, callback control, or refcount takeover. Therefore this is best handled as Actionable Moderate at minimum, with manual review required, rather than automatically classifying it as a strong Important vulnerability.

## 5. One-sentence report phrase

A race in netfilter conntrack expectation cleanup can leave an expectation with a stale exp master pointer after the master conntrack is released, creating a network influenced UAF candidate with at least kernel crash DoS impact and requiring manual review.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED. YES REQUIRES MANUAL CHECK.

Reason: network-influenced netfilter packet path plus explicit stale pointer lifetime race makes this a UAF candidate, even though the supplied patch does not prove a practical privilege escalation primitive.

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

Patch: netfilter: nf_conntrack_expect: use conntrack GC to reap expectations [ Upstream
Commit: 7ec786f4230c2a9b2eaf97a2d45368933b49d2b2
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=7ec786f4230c2a9b2eaf97a2d45368933b49d2b2

Changed files:
  include/net/netfilter/nf_conntrack_expect.h
  include/uapi/linux/netfilter/nf_conntrack_common.h
  net/netfilter/nf_conntrack_core.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=7ec786f4230c2a9b2eaf97a2d45368933b49d2b2

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

The original Linux kernel CVE announcement for CVE-2026-80668 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80668

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:H
  The Best / paranoid CVSS vector: AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
  The Best / paranoid CVSS score: 8.1

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).