[CVE-2026-98089][MODERATE REGULAR] bonding: alb: fix uninitialized transport header access in alb_determine_nd() [ Upstream

[CVE-2026-98089][MODERATE REGULAR] bonding: alb: fix uninitialized transport header access in alb_determine_nd() [ Upstream

[AL-KERNEL]

CVE: CVE-2026-98089
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: bonding: alb: fix uninitialized transport header access in alb_determine_nd() [ Upstream
Commit: e39cf90bd856443542b97933289749fca07476bf
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=e39cf90bd856443542b97933289749fca07476bf
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98089
Analysis date: Fri, 25 Sep 2026 09:55:13 -0400
ActionableScore: 2
ActionableScore lower bound: unknown
Actionable bucket: Ordinary Moderate
Manual review required: NO

Summary:
No one-sentence report phrase was found.

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

The original Linux kernel CVE announcement for CVE-2026-98089 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98089

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: NO

A detailed explanation of the methodology and priority rules is included
at the end of this message.

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

CVE-2026-98089	MODERATE	https://www.kernelcve.org/list/?q=CVE-2026-98089 CHECK WITH IMPACT FROM ORIG NN IMPORTANT	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:A/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H';CWE-125;CWE-908;CWE-665;BEST CVSS score: '5.3';DESCR 'An out of bounds read in the bonding ALB and TLB transmit path can occur because alb_determine_nd uses skb transport_header to locate an ICMPv6 header even when that offset has not been initialized. A network adjacent attacker may trigger the affected path with IPv6 traffic that is forwarded or otherwise transmitted through a bond configured in balance alb or balance tlb mode. The invalid read can cause incorrect Neighbor Discovery packet classification or a kernel fault resulting in denial of service. For the CVSS the PR:N is selected because a remote network peer does not need local access when it can send traffic through an affected forwarding or transmission path. The issue is network adjacent rather than generally Internet reachable because it depends on a specific bonding configuration and suitable local network topology. No confidentiality or integrity impact is assigned because the patch shows only an out of bounds header read whose result is used for packet classification and does not demonstrate data disclosure or a write primitive.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 2)	YES	WRITE OOB SIMPLEFIX NETWORK SKB LINUS IPV6 PACKET  LOWERED_FROM_HIGH_BASED_ON_GUESSCVSS  DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN4	NO	NO	checked

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

ActionableScore=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: 2
* Paranoid score: 2
* Final recommended bucket: **Ordinary Moderate**::

2. Signal breakdown

* +2 Directly network-triggerable path. A network-adjacent peer can supply IPv6 traffic that reaches the affected transmit path when the target already uses bonding in balance-alb or balance-tlb mode and forwards or transmits the packet through that bond.
* +0 Invalid out-of-bounds read. The patch establishes an invalid read through an uninitialized skb transport_header, but no attacker-controlled write, object replacement, lifetime violation, or disclosure path is shown.
* +0 Kernel crash not independently awarded. An invalid read can potentially fault, but the supplied evidence does not establish a reliable panic or host-wide crash.
* +0 Confidentiality not awarded. The out-of-bounds value is only compared with ICMPv6 Neighbor Discovery type constants. No bytes are returned to userspace, sent over the network, or otherwise disclosed.
* +0 Integrity not awarded. The vulnerable operation reads memory only and does not establish a write primitive or security-state modification.
* +0 Strong exploitation leverage not awarded. Controlled reclaim, arbitrary read or write, callback influence, type confusion, and privilege escalation are not established.
* +0 No negative privilege penalty. The attacker need not hold host administrative privileges to send traffic to a preconfigured vulnerable forwarding or transmission path.
* +0 No niche-subsystem penalty. Bonding ALB and TLB configuration is required, but the supplied context does not establish that the attacker must create or configure the bond.

3. Reachability analysis

The evaluated attacker is a network-adjacent peer, not a local administrator. The vulnerable operation can be reached when a host has an existing bonding interface configured for balance-alb or balance-tlb and IPv6 traffic is forwarded or transmitted through that bond.

The attacker does not need CAP_NET_ADMIN, raw socket access, or AF_PACKET access on the victim. Those interfaces are examples of paths that can create skb objects with an uninitialized transport_header, while forwarded traffic is also explicitly identified by the commit as affected.

The target must already have the relevant bonding configuration and a suitable IPv6 forwarding or transmit topology. This is a deployment prerequisite, but it is not evidence that the attacker requires host-admin-equivalent privilege. No namespace-specific capability checks or complete namespace-scoped trigger chain are shown.

4. Primitive and severity interpretation

The exact primitive is an out-of-bounds kernel read caused by using icmp6_hdr(skb) when skb transport_header is not initialized. The patch replaces that lookup with direct parsing immediately after the IPv6 header after confirming that the required bytes are linear and available.

This is not a UAF, refcount error, double release, stale active object, or ownership violation. It is not an out-of-bounds write. The read result is used only to classify a packet as an IPv6 Neighbor Advertisement or Neighbor Solicitation, so the visible consequence is incorrect packet classification or a possible invalid-memory fault.

PrimitiveClass is CLASS_C because the demonstrated behavior is invalid-state and crash or DoS relevant behavior without an independently useful corruption primitive. ImportantCandidate is NO because the patch does not establish meaningful exploitation leverage beyond the invalid read. AutoDowngradeAllowed is YES because no unresolved active-object lifetime, write, disclosure, authorization, or security-boundary primitive is demonstrated.

Likely operational severity is ordinary Moderate. It should still be reviewed before automated closure because a network-adjacent malformed-packet path reaches kernel memory parsing, but the evidence supports a constrained read-only DoS concern rather than privilege escalation or disclosure.

5. One-sentence report phrase

A network-adjacent attacker may trigger an out-of-bounds kernel read in the bonding ALB or TLB IPv6 transmit path because an uninitialized skb transport_header is used to locate an ICMPv6 header, potentially causing packet misclassification or denial of service.

6. Manual review recommendation

MANUAL CHECK RECOMMENDED

The issue is network-triggerable in a specific bonding deployment and contains an explicit kernel out-of-bounds read, but the supplied patch does not establish data disclosure, memory modification, a reliable crash, or privilege escalation.

7. Call-site confidence

Call-site confidence: medium

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

Patch: bonding: alb: fix uninitialized transport header access in alb_determine_nd() [ Upstream
Commit: e39cf90bd856443542b97933289749fca07476bf
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=e39cf90bd856443542b97933289749fca07476bf

Changed files:
  drivers/net/bonding/bond_alb.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=e39cf90bd856443542b97933289749fca07476bf

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

The original Linux kernel CVE announcement for CVE-2026-98089 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98089

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: Not available
  The Best / paranoid CVSS vector: AV:A/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS score: 5.3

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: unknown
  Paranoid ActionableScore: 2

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).