[CVE-2026-80636][MODERATE 7.0] netfilter: conntrack: revert ct extension genid infrastructure [ Upstream

[CVE-2026-80636][MODERATE 7.0] netfilter: conntrack: revert ct extension genid infrastructure [ Upstream

[AL-KERNEL]

CVE: CVE-2026-80636
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: netfilter: conntrack: revert ct extension genid infrastructure [ Upstream
Commit: 6bba4846f196d081bf553391d12b5a73dcc48685
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=6bba4846f196d081bf553391d12b5a73dcc48685
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80636
Analysis date: Fri, 28 Aug 2026 07:18:29 -0400
ActionableScore: 5
ActionableScore lower bound: 3
Actionable bucket: Actionable Moderate at minimum
Manual review required: YES

Summary:
No one-sentence report phrase was found.

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

The original Linux kernel CVE announcement for CVE-2026-80636 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80636

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.

======================================================================
AL-KERNEL CLASSIFICATION RESULT
======================================================================

CVE-2026-80636	MODERATE	CHECK WITH IMPACT FROM ORIG NN IMPORTANT	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H';**CWE-476;CWE-703;CWE-362;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '4.7';DESCR 'The conntrack extension genid logic could make nf_ct_ext_find return NULL for unconfirmed conntrack entries even when later code expected a valid extension and dereferenced it. This can lead to a NULL pointer dereference in netfilter conntrack processing and crash the kernel. For the CVSS the PR:L is used in the paranoid score because CAP_NET_ADMIN or equivalent netfilter control may be delegated to a container root, service account, or reduced capability administrator in some deployments. The issue is not clearly exploitable by remote packets alone because reliable triggering appears to require control plane changes affecting conntrack extensions, helpers, or timeouts. Impact is denial of service via kernel crash. No concrete UAF, OOB write, arbitrary write, or information leak primitive is proven by the patch context.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 4)	YES	REMOTE LOCK DANGER INIT SIMPLEFIX NETFILTER RACE SKB  LOWERED_FROM_HIGH_BASED_ON_GUESSCVSS  DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5	YES	NO	checked

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

ActionableScore=5
ActionableScoreLower=3

1. ActionableScore
* Conservative score: 3
* Paranoid score: 5
* Final recommended bucket: **Actionable Moderate at minimum**::

2. Signal breakdown
* Weak/indirect corruption candidate: +1. `nf_ct_ext_find()` could return NULL for unconfirmed conntracks when later code expects a valid conntrack extension and dereferences it. This is treated as NULL dereference / weak invalid-object state, not strong memory corruption.
* Real lifetime / RCU concern: +1. The removed genid logic was tied to stale extension visibility, unconfirmed conntracks, queued skb lifetime, and RCU cleanup semantics, so the area deserves lifetime review even though a concrete UAF primitive is not proven here.
* Reliable kernel crash / strong DoS: +1. The commit explicitly says unchecked NULL dereference could lead to crash.
* Common networking core or packet-processing path: +1. Conntrack extensions are part of netfilter packet processing and firewall/NAT state handling.
* Broad/default/common subsystem: +1. Netfilter conntrack is widely deployed on firewalls, container hosts, NAT systems, and general Linux networking stacks.
* Requires CAP_NET_ADMIN in typical deployments: -2 for the conservative score. Reliable triggering appears to involve conntrack helper or timeout control-plane changes, not only remote packets.
* Paranoid privilege interpretation: the -2 penalty is not applied for the higher score because CAP_NET_ADMIN may be delegated to container root, a service account, or a reduced-capability administrator in real deployments.

3. Reachability analysis
The likely trigger requires local control over netfilter or conntrack helper/timeout state, normally requiring CAP_NET_ADMIN. Remote packets alone are not clearly sufficient from the patch, although packet processing is involved because the bug affects unconfirmed conntracks and extension lookup in the datapath. Namespaces and containers matter: a container or service with delegated CAP_NET_ADMIN may be able to reach the affected control plane without being equivalent to full host root. The path is in a common networking subsystem, but the specific trigger depends on affected conntrack extension genid behavior and helper/timeout usage.

Call-site confidence: medium. The patch shows the extension lookup and conntrack confirmation paths, but the exact unchecked dereference sites are not included in the provided diff.

4. Severity interpretation
This is best treated as Actionable Moderate in paranoid triage, not as a Strong Important candidate based on the available evidence. The realistic demonstrated impact is kernel crash / DoS from NULL dereference. The patch context raises lifetime and RCU concerns, but it does not show attacker-controlled reclaim, UAF reuse, arbitrary write, type confusion, or an information leak. Therefore C:N/I:N remains appropriate for CVSS-style impact unless additional evidence shows a real memory corruption primitive.

5. One-sentence report phrase
Conntrack extension genid handling could hide extensions on unconfirmed conntracks and let later netfilter code dereference NULL, causing a kernel crash when conntrack helper or timeout control-plane changes interact with packet processing.

6. Manual review recommendation
MANUAL CHECK REQUIRED. YES REQUIRES MANUAL CHECK because this is netfilter datapath-adjacent conntrack lifetime code with possible namespace-delegated CAP_NET_ADMIN reachability, even though the currently supported impact is DoS rather than proven privilege escalation.

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

Patch: netfilter: conntrack: revert ct extension genid infrastructure [ Upstream
Commit: 6bba4846f196d081bf553391d12b5a73dcc48685
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=6bba4846f196d081bf553391d12b5a73dcc48685

Changed files:
  include/net/netfilter/nf_conntrack_extend.h
  net/netfilter/nf_conntrack_core.c
  net/netfilter/nf_conntrack_extend.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=6bba4846f196d081bf553391d12b5a73dcc48685

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

The original Linux kernel CVE announcement for CVE-2026-80636 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80636

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:H/PR:H/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS score: 4.7

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: 3
  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: NO
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).