[CVE-2026-64116][MODERATE REGULAR] ipv6: ioam: add NULL check for idev in ipv6_hop_ioam() [ Upstream

[CVE-2026-64116][MODERATE REGULAR] ipv6: ioam: add NULL check for idev in ipv6_hop_ioam() [ Upstream

[AL-KERNEL]

CVE: CVE-2026-64116
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: ipv6: ioam: add NULL check for idev in ipv6_hop_ioam() [ Upstream
Commit: c7e8971abd70e9d022f1c251ba2508f8dc7f2db8
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=c7e8971abd70e9d022f1c251ba2508f8dc7f2db8
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64116
Analysis date: Sun, 19 Jul 2026 20:46:51 -0400
ActionableScore: 4
ActionableScore lower bound: 3
Actionable bucket: Borderline, manual review recommended
Manual review required: YES

Summary:
A network-triggerable NULL pointer dereference in IPv6 IOAM Hop-by-Hop processing can crash the kernel if an IOAM packet is handled while IPv6 state is concurrently removed from the receiving interface.

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

The original Linux kernel CVE announcement for CVE-2026-64116 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64116

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-2026-64116	MODERATE	CHECK WITH IMPACT FROM ORIG NN MODERATE	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-476;CWE-362;CWE-703;Other CVSS 'AV:A/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '5.9';DESCR 'ipv6_hop_ioam can dereference a NULL inet6_dev pointer because __in6_dev_get(skb dev) may return NULL while addrconf_ifdown clears dev ip6_ptr through RCU during interface teardown. A remote sender can potentially trigger the fault by delivering an IPv6 packet with an IOAM Hop-by-Hop option while the receiving interface is losing its IPv6 configuration, causing a kernel crash. For the CVSS the PR:N is used because the attacker does not need an account on the target and only needs packet reachability to the IPv6 IOAM processing path. The issue is network reachable, but practical exploitation is timing dependent and likely limited to local or controlled IOAM enabled network domains where such Hop-by-Hop options are accepted. Impact is denial of service only because the patch supports a NULL pointer dereference rather than a demonstrated UAF, OOB write, information leak, or privilege escalation primitive.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline, manual review recommended (with actual score 4)	YES	REMOTE NULLPTR SIMPLEFIX NETWORK SKB HARDWARE IPV6  DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5	YES	NO	checked

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

ActionableScore=4
ActionableScoreLower=3

## 1. ActionableScore

* Conservative score: 3
* Paranoid score: 4
* Final recommended bucket: **Borderline, manual review recommended**::

## 2. Signal breakdown

Conservative signals:

* Remote reachable / network-triggerable: +2
  IPv6 Hop-by-Hop IOAM option processing is in the packet receive path and can potentially be reached by packets delivered to the affected interface.

* Reliable kernel crash / strong DoS: +1
  The patch fixes a NULL pointer dereference of `__in6_dev_get(skb->dev)->cnf.ioam6_enabled`, which can crash the kernel if hit.

* Hard or unreliable race / special timing required: -1
  Triggering requires packet processing to coincide with interface IPv6 teardown where `addrconf_ifdown()` clears `dev->ip6_ptr`.

* Rare AND difficult-to-reach subsystem/configuration: -1
  IOAM Hop-by-Hop processing is not a typical Internet-exposed path and is usually relevant in controlled IPv6/IOAM domains.

* Common networking packet-processing path: +1
  Although IOAM itself is specialized, the vulnerable code is still in IPv6 extension-header packet processing.

Conservative total: 3

Paranoid adjustment:

* Do not apply the rare-subsystem penalty in the paranoid score because this is still packet-triggered kernel networking code and the packet may be externally supplied in an IOAM-enabled/internal network.

Paranoid total: 4

No memory-corruption or LPE points are awarded. The patch shows a NULL dereference, not UAF, OOB write, double free, refcount takeover, arbitrary write, or attacker-controlled object reuse.

## 3. Reachability analysis

An attacker needs packet reachability to an affected IPv6 interface processing IOAM Hop-by-Hop options. No local account on the target is required for the network-triggered interpretation, so PR:N is reasonable for CVSS-style triage.

The realistic trigger is timing-dependent: an IOAM packet must be processed while the interface is losing IPv6 configuration and `dev->ip6_ptr` can be observed as NULL. This makes exploitation unreliable compared with ordinary protocol parser crashes.

Namespaces and containers mainly matter on the defender side if untrusted tenants can influence interface teardown or generate internal IOAM traffic. However, the patch itself does not show a local privilege-escalation primitive.

The path is not normally public-Internet exposed. IOAM is typically used in controlled provider, data-center, or lab networks, and Hop-by-Hop options may be filtered or ignored by many network paths.

## 4. Severity interpretation

This behaves like an actionable Borderline/Moderate network DoS issue, not an Important-class memory corruption bug.

The theoretical risk is a remote or adjacent sender causing a kernel crash through a NULL pointer dereference during a narrow teardown race. The realistic evidence supports DoS only. There is no demonstrated confidentiality impact, integrity impact, privilege escalation path, UAF reclaim, stale callback, type confusion, or write primitive.

Because it is network-reachable kernel packet-processing code with an RCU/race component, it should not be blindly auto-closed, but the score remains below Actionable Moderate/Important because the primitive is only NULL dereference and timing-dependent.

## 5. One-sentence report phrase

A network-triggerable NULL pointer dereference in IPv6 IOAM Hop-by-Hop processing can crash the kernel if an IOAM packet is handled while IPv6 state is concurrently removed from the receiving interface.

## 6. Manual review recommendation

MANUAL CHECK RECOMMENDED

Reason: the issue is network-triggerable and race-dependent in IPv6 packet processing, but the demonstrated primitive is limited to NULL pointer dereference and DoS.

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

Patch: ipv6: ioam: add NULL check for idev in ipv6_hop_ioam() [ Upstream
Commit: c7e8971abd70e9d022f1c251ba2508f8dc7f2db8
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=c7e8971abd70e9d022f1c251ba2508f8dc7f2db8

Changed files:
  net/ipv6/exthdrs.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=c7e8971abd70e9d022f1c251ba2508f8dc7f2db8

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

The original Linux kernel CVE announcement for CVE-2026-64116 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64116

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:A/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: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: 3
  Paranoid ActionableScore: 4

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).