[CVE-2026-97417][MODERATE REGULAR] netfilter: nf_conntrack: use get_unaligned_be32() in tcp_sack() [ Upstream

[CVE-2026-97417][MODERATE REGULAR] netfilter: nf_conntrack: use get_unaligned_be32() in tcp_sack() [ Upstream

[AL-KERNEL]

CVE: CVE-2026-97417
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: netfilter: nf_conntrack: use get_unaligned_be32() in tcp_sack() [ Upstream
Commit: 7ecfa46a536578a7ed335ddf31a854127268c27c
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=7ecfa46a536578a7ed335ddf31a854127268c27c
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-97417
Analysis date: Thu, 24 Sep 2026 15:13:47 -0400
ActionableScore: 3
ActionableScore lower bound: 2
Actionable bucket: Borderline / manual review recommended
Manual review required: YES

Summary:
No one-sentence report phrase was found.

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

The original Linux kernel CVE announcement for CVE-2026-97417 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-97417

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 REGULAR
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-2026-97417	MODERATE	https://www.kernelcve.org/list/?q=CVE-2026-97417 CHECK WITH IMPACT FROM ORIG NN MODERATE	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H';CWE-704;CWE-758;Other CVSS 'AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '7.5';DESCR 'A remote denial of service can occur in the nf_conntrack TCP timestamp fast path because tcp_sack dereferences a TCP option pointer as a 32 bit value without guaranteed alignment. A remote attacker may send a TCP segment with a timestamp only option and trigger an alignment fault on architectures that do not safely handle unaligned accesses. For the CVSS the PR:N because no victim side account or local code execution is required beyond network reachability to a system that processes the traffic through nf_conntrack. The issue is network reachable when connection tracking is enabled and reachable TCP traffic is inspected. Impact is kernel crash or loss of packet processing availability. No information disclosure integrity impact or privilege escalation primitive is demonstrated by the affected access. YES REQUIRES MANUAL CHECK';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline / manual review recommended (with actual score 3)	YES	REMOTE NETFILTER NETWORK  INCREASED_TO_MODERATE7_BASED_ON_GUESSCVSS DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN4	NO	NO	checked

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

ActionableScore=3
ActionableScoreLower=2
PrimitiveClass=CLASS_C
RealUAF=NO
HostAdminRequired=NO
NamespaceScopedPrivilege=UNKNOWN
ImportantCandidate=NO
ManualReview=RECOMMENDED
AutoDowngradeAllowed=YES

1. ActionableScore

* Raw conservative score: 2
* Conservative score: 2
* Raw paranoid score: 3
* Paranoid score: 3
* Final recommended bucket: **Borderline / manual review recommended**::

No floor or cap was applied.

2. Signal breakdown

Conservative signals:

* +2 Remote reachable / directly network-triggerable. A remote peer can provide a TCP packet containing the timestamp-only option sequence. The packet can reach tcp_sack when connection tracking processes the traffic. No local account or victim-side code execution is needed.
* +0 No reliable kernel crash point in the conservative score. The patch establishes an unsafe unaligned access, but the supplied evidence does not establish that every affected architecture turns it into a fatal kernel fault.

Paranoid-only signal:

* +1 Potential strong DoS on alignment-sensitive architectures. The direct __be32 pointer dereference may generate an alignment exception when the TCP option pointer is not four-byte aligned. A kernel exception in conntrack packet processing can result in an Oops, panic, or loss of packet-processing availability depending on the architecture and exception handling configuration.

Negative signals:

* No host-admin penalty. Host-admin privilege is not required for an external peer to send the triggering packet.
* No niche-subsystem penalty. Netfilter connection tracking is broadly deployed and can inspect ordinary TCP traffic. The alignment-sensitive architecture condition is material, but it is not sufficient evidence for a rare-hardware penalty.
* No race penalty. This is an ordered packet parsing condition, not a concurrency race.

Important non-awarded signals:

* No UAF, stale object, refcount misuse, double release, or lifetime violation is established.
* No out-of-bounds access is established. The read is unsafe because of alignment, not because ptr exceeds the TCP option bounds.
* No attacker-controlled write, arbitrary write, object replacement, callback influence, or controlled reclaim is demonstrated.
* No confidentiality impact is established because the loaded value is only compared with a fixed timestamp-option signature.
* No integrity impact is established because the affected operation is read-only.
* No privilege escalation or security-boundary bypass is established.
* No additional availability point was awarded for the same possible alignment fault.

3. Reachability analysis

The evaluated attacker is a remote network peer. The attacker can send a TCP segment with a timestamp-only option layout that reaches the conntrack TCP parser. The vulnerable fast path performs a direct 32-bit dereference of the option-stream pointer without a guaranteed four-byte alignment.

The complete trigger does not require host administration, a local account, CAP_NET_ADMIN, a namespace capability, or local control-plane access. Therefore HostAdminRequired is NO.

Connection tracking must be enabled and the attacker traffic must traverse it. This is a deployment prerequisite, not an attacker privilege requirement. The practical consequence also depends on an architecture or kernel configuration where the unaligned access is not safely handled or fixed up. The patch itself identifies this alignment assumption as invalid, but the supplied input does not establish affected architecture families or a confirmed fatal exception behavior.

NamespaceScopedPrivilege is UNKNOWN because namespaces are not relevant to the demonstrated external packet trigger and no namespace capability chain is involved.

4. Primitive and severity interpretation

The exact primitive is an unaligned 32-bit read from a TCP option stream in nf_conntrack tcp_sack. The option stream does not guarantee four-byte alignment, while the old code dereferenced ptr through a __be32 pointer. This is an invalid-state and potential alignment-fault condition.

This is not an active structured-object lifetime issue, fixed stale storage issue, UAF, refcount corruption, repeated release, or ownership violation. There is no first lifetime operation and no second lifetime-mutating operation.

PrimitiveClass is CLASS_C because the demonstrated behavior is an invalid access that can cause a fault or DoS on alignment-sensitive systems. RealUAF is NO.

The practical demonstrated security consequence is remote packet-processing failure or potential kernel crash on affected architectures. The stronger consequence of host-wide kernel panic is plausible but not directly demonstrated by the supplied patch or advisory evidence. There is no patch-supported leverage beyond the potential fault itself.

ImportantCandidate is NO because no meaningful memory-corruption, authorization, ownership, disclosure, or post-fault exploitation primitive is established. AutoDowngradeAllowed is YES because the issue is a constrained read-only alignment defect with no unresolved UAF, write primitive, or security-boundary bypass.

Likely operational severity is ordinary-to-borderline Moderate. It merits validation on affected strict-alignment architectures and deployed conntrack configurations, but the patch does not support Important-class classification.

5. One-sentence report phrase

A remote peer may trigger an alignment fault in nf_conntrack TCP option parsing by sending a timestamp-only TCP option sequence that reaches tcp_sack with an unaligned option pointer.

6. Manual review recommendation

MANUAL CHECK RECOMMENDED

Confirm whether deployed target architectures fault on this unaligned access, whether the resulting fault can panic the kernel, and whether externally reachable traffic traverses nf_conntrack.

7. Call-site confidence

Call-site confidence: medium

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

Patch: netfilter: nf_conntrack: use get_unaligned_be32() in tcp_sack() [ Upstream
Commit: 7ecfa46a536578a7ed335ddf31a854127268c27c
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=7ecfa46a536578a7ed335ddf31a854127268c27c

Changed files:
  net/netfilter/nf_conntrack_proto_tcp.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=7ecfa46a536578a7ed335ddf31a854127268c27c

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

The original Linux kernel CVE announcement for CVE-2026-97417 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-97417

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:L/PR:N/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS score: 7.5

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: 2
  Paranoid ActionableScore: 3

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 REGULAR

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).