[CVE-2026-99088][MODERATE REGULAR] net: openvswitch: validate transport header presence in set_ipv6_addr [ Upstream

[CVE-2026-99088][MODERATE REGULAR] net: openvswitch: validate transport header presence in set_ipv6_addr [ Upstream

[AL-KERNEL]

CVE: CVE-2026-99088
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: net: openvswitch: validate transport header presence in set_ipv6_addr [ Upstream
Commit: b7b80d204abdc258006f9e17c92b363ab13bb599
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=b7b80d204abdc258006f9e17c92b363ab13bb599
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99088
Analysis date: Mon, 26 Oct 2026 22:50:24 -0400
ActionableScore: 1
ActionableScore lower bound: 0
Actionable bucket: Ordinary Moderate
Manual review required: NO

Summary:
Open vSwitch IPv6 fragment rewriting can trigger a harmless transport-header debug warning, with host DoS only under a warning-to-panic policy.

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

The original Linux kernel CVE announcement for CVE-2026-99088 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99088

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-2026-99088	MODERATE	https://www.kernelcve.org/list/?q=CVE-2026-99088 CHECK WITH IMPACT FROM ORIG NN MODERATE | AEGIS IMPACT MODERATE AEGIS_AS=0 LEGACY=MODERATE RESULT=SAME (final reconciliation agrees; DECISION: both MODERATE)	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-457;CWE-665;CWE-754;Other CVSS 'AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '5.3';DESCR 'Open vSwitch IPv6 address rewriting can evaluate skb_transport_offset for a non first IPv6 fragment even though parsing returned before setting the transport header. The demonstrated effect is a CONFIG_DEBUG_NET warning and the patch context explicitly indicates that normal processing is otherwise harmless. There is no supported OOB access, UAF, information leak, arbitrary write, or privilege escalation primitive. For the CVSS the PR:N value in the paranoid vector applies only when an existing Open vSwitch rule lets an adjacent sender trigger the path with crafted IPv6 fragments. The higher availability impact additionally assumes panic_on_warn or a similar policy that converts the warning into a host crash. Automated impact decision path. The original SimpleNet classifier selected MODERATE_KPANIC. The primary LLM estimated paranoid CVSS 5.3 and the production ActionableScore returned 1 with recommendation Ordinary Moderate. The production rules then evaluated CVSS thresholds and ActionableScore thresholds. Recorded rule transitions were CVSS and initial triage stage MODERATE_KPANIC to MODERATE because the CVSS score, vector or bug class threshold rule was applied. The legacy KP specialist has no review artifact for this run. The legacy FD or DH downgrade specialist has no review artifact for this run. Exact triggered rule markers were DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS_AND_CIANNH. The independent weaker Aegis shadow evaluated CVSS 0.0 and ActionableScore 0 with primitive class CLASS_C and manual review REQUIRED. Its independently reconciled impact was MODERATE. The shadow agreed with the final production impact and aggregation did not change that impact. The final reported impact is MODERATE.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 1)	MAYBE	OOB DANGER SKB HARDWARE LINUS IPV6 SYZBOT  DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS_AND_CIANNH	-	-	checked

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

ActionableScore=1
ActionableScoreLower=0
PrimitiveClass=NONE
RealUAF=NO
HostAdminRequired=UNKNOWN
NamespaceScopedPrivilege=UNKNOWN
ImportantCandidate=NO
ManualReview=RECOMMENDED
AutoDowngradeAllowed=YES
RequiresHostUID0=UNKNOWN
AuthorizationDecisionBypass=NO
ProtectedResourceImpact=NONE
B4PendingReview=NO
B4PendingConfirmed=NO

1. ActionableScore

* Raw base score: 0.
* Conservative score: 0; no floor or cap applied.
* Raw paranoid score: 1.
* Paranoid score: 1; conditional panic from the demonstrated WARN under `panic_on_warn`.
* Final recommended bucket: **Ordinary Moderate**::

2. Signal breakdown

* Base +0: `skb_transport_offset()` evaluates an unset transport-header offset and emits a `CONFIG_DEBUG_NET` warning. No invalid memory access or state mutation is shown.
* Paranoid +1: strong DoS is possible only when policy such as `panic_on_warn` converts the warning into a host panic.
* No additional availability point: it would duplicate that same conditional panic.
* No checksum-corruption signal: for `NEXTHDR_FRAGMENT`, the old function computes `transport_len` but reaches none of the TCP/UDP/ICMPv6 checksum-update branches.
* No OOB write, UAF, disclosure, authorization bypass, B5-R retry accumulation, shared-backing write, or active structured-state corruption is shown.
* Remote/adjacent reachability is not scored: crafted fragments require an already configured Open vSwitch action path.

3. Reachability analysis

The visible reproducer uses `OVS_PACKET_CMD_EXECUTE` over generic netlink, but the supplied evidence does not resolve the effective capability or namespace requirements for the complete setup and execution chain. An adjacent sender could exercise an existing rewrite rule, but creation of that rule is prior control-plane configuration. Namespace-scoped completion and host-admin-only triggering are therefore both unproven. No race, retry accumulation, special hardware, or boot prerequisite exists beyond optional debug/panic policy.

4. Primitive and severity reading

The exact behavior is an uninitialized transport-offset metadata read that triggers a debug assertion. It is neither a memory-corruption primitive nor corrupted-state consumption: the fragment protocol causes no subsequent checksum write. The shown effect is a warning; host panic is conditional on warning policy. Consequently, there is no Important-preserving primitive, and automatic downgrade is allowed.

5. One-sentence report phrase

Open vSwitch IPv6 fragment rewriting can trigger a harmless transport-header debug warning, with host DoS only under a warning-to-panic policy.

6. Manual review advice

MANUAL CHECK RECOMMENDED

Verify product `CONFIG_DEBUG_NET`/`panic_on_warn` policy and whether an unprivileged or adjacent actor can reach a preconfigured rewrite path.

7. Call-site confidence

Call-site confidence: high

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

Patch: net: openvswitch: validate transport header presence in set_ipv6_addr [ Upstream
Commit: b7b80d204abdc258006f9e17c92b363ab13bb599
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=b7b80d204abdc258006f9e17c92b363ab13bb599

Changed files:
  include/linux/skbuff.h
  net/openvswitch/actions.c
  net/openvswitch/datapath.c
  net/netlink/genetlink.c
  net/netlink/af_netlink.c
  net/socket.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=b7b80d204abdc258006f9e17c92b363ab13bb599

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

The original Linux kernel CVE announcement for CVE-2026-99088 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99088

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:L/PR:H/UI:N/S:U/C:N/I:N/A:L
  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: 0
  Paranoid ActionableScore: 1

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).