[CVE-2026-98491][MODERATE 7.0] net: openvswitch: conntrack: avoid modifying shared unconfirmed ct entry

[AL-KERNEL <alkernel@kernelcve.org>]

CVE: CVE-2026-98491
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: net: openvswitch: conntrack: avoid modifying shared unconfirmed ct entry
Commit: e0fa5ea434b7e8467ef3adc64e3858b1ca2a642d
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=e0fa5ea434b7e8467ef3adc64e3858b1ca2a642d
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98491
Analysis date: Mon, 19 Oct 2026 00:27:39 -0400
ActionableScore: 3
ActionableScore lower bound: unknown
Actionable bucket: Borderline / manual review recommended
Manual review required: YES

Summary:
A shared unconfirmed Open vSwitch conntrack entry can have its extension storage replaced while an expectation retains a stale pointer, causing a destruction-path use after free and potential kernel crash, although a practical below-host-admin packet-only trigger is not established.

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ABOUT THIS REPORT
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The original Linux kernel CVE announcement for CVE-2026-98491 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98491

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.

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AL-KERNEL CLASSIFICATION RESULT
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CVE-2026-98491	MODERATE	https://www.kernelcve.org/list/?q=CVE-2026-98491 CHECK WITH IMPACT FROM ORIG NN MODERATE | AEGIS IMPACT MODERATE_KPANIC AEGIS_AS=2 LEGACY=MODERATE_KPANIC RESULT=SAME V39_AEGIS_ONE_STEP_UP=MODERATE->MODERATE_KPANIC (final reconciliation agrees; DECISION: both MODERATE_KPANIC)	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:A/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H';*CWE-416;CWE-362;CWE-662;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:L/I:L/A:H';BEST CVSS score: '7.5';DESCR 'A race in Open vSwitch conntrack handling can occur when cloned skbs share the same unconfirmed conntrack entry and both clones attempt to commit it with different extension sets. One commit can wire a helper extension into an expectation list while another commit changes the shared extension storage, leaving a stale pointer that can be dereferenced during the later destruction path and cause a use after free. The confirmed impact is at least a kernel crash and denial of service. Because this is a real stale pointer memory safety condition, confidentiality and integrity impact or privilege escalation may also be possible, although no reliable write primitive or working escalation path is established. For the CVSS the PR:N value is used in the paranoid assessment because an attacker may only need packet access after a vulnerable Open vSwitch pipeline has already been configured by an administrator. The attack is considered adjacent network rather than unrestricted remote network because it depends on access to the affected virtual switch or connected network segment. Attack complexity is high because two cloned packets must reach conflicting commit paths in the required order and race window. The commit states that no practical network pipeline requiring this behavior is currently known, so real world reachability and exploitability require manual validation. Automated impact decision path. The original SimpleNet classifier selected MODERATE. The primary LLM estimated paranoid CVSS 7.5 and the production ActionableScore returned 3 with recommendation Borderline / manual review recommended. The production rules then evaluated CVSS thresholds and ActionableScore thresholds. Recorded rule transitions were CVSS and initial triage stage MODERATE to MODERATE_KPANIC because the CVSS score, vector or bug class threshold rule was applied. ActionableScore thresholds stage MODERATE_KPANIC to MODERATE because the ActionableScore threshold rule was applied. final reconciliation stage MODERATE to MODERATE_KPANIC because the cross model evidence reconciliation 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 INCREASED_TO_MODERATE7_BASED_ON_GUESSCVSS and DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN4 and V39_AEGIS_ONE_STEP_UP and MANUAL_REVIEW_REQUIRED. The independent weaker Aegis shadow evaluated CVSS 2.7 and ActionableScore 2 with primitive class CLASS_B and manual review REQUIRED. Its independently reconciled impact was MODERATE_KPANIC. Cross model aggregation changed the production result under an enabled evidence gated merge rule. The final reported impact is MODERATE_KPANIC.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline / manual review recommended (with actual score 3)	MAYBE	REMOTE DANGER NETFILTER UAF SKB LINUS  INCREASED_TO_MODERATE7_BASED_ON_GUESSCVSS DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN4 KPANIC V39_AEGIS_ONE_STEP_UP MANUAL_REVIEW_REQUIRED	-	-	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=3
PrimitiveClass=CLASS_B
RealUAF=YES
HostAdminRequired=UNKNOWN
NamespaceScopedPrivilege=UNKNOWN
ImportantCandidate=NO
ManualReview=RECOMMENDED
AutoDowngradeAllowed=YES
RequiresHostUID0=UNKNOWN
AuthorizationDecisionBypass=NO
ProtectedResourceImpact=NONE
B4PendingReview=NO
B4PendingConfirmed=NO

1. ActionableScore

* Raw conservative score: 3
* Conservative score: 3
* Raw paranoid score: 3
* Paranoid score: 3
* No floor or cap was applied.
* Final recommended bucket: **Borderline / manual review recommended**::

2. Signal breakdown

* +2 Real UAF. Adding a different extension to a shared unconfirmed conntrack entry can relocate or replace extension storage while an expectation list retains a pointer into the old storage. The pointer is later consumed after its lifetime has ended.
* +1 Reliable kernel crash or strong DoS. Dereferencing the stale extension pointer during destruction can realistically produce an Oops or kernel crash.
* +0 Remote or adjacent-network reachability. Packet processing reaches the affected code, but the commit explicitly says that no practical pipeline requiring both clone commits in the same zone is known. A usable packet-only trigger is not established.
* +0 Active-object lifetime manipulation. Different extension sets modify active conntrack state, but the evidence does not establish that a below-host-admin attacker controls the required clone and commit pipeline or its lifetime transitions.
* +0 Structured stale-object leverage. The stale pointer is stored in an expectation structure, but the demonstrated consumption occurs on the destruction path. No distinct post-reuse field processing, callback dispatch, controlled replacement, or useful write is shown.
* +0 Race penalty. The required ordering is described, but the evidence does not establish a narrow or externally uncontrollable timing window sufficient for a minus one penalty.
* +0 Privilege penalty. Host-admin-equivalent privilege is not positively established for the complete trigger, so no speculative privilege penalty is applied.
* Controlled reclaim, arbitrary write, disclosure, repeated release, refcount takeover, and privilege escalation are not demonstrated.
* No additional Availability point is awarded because it would duplicate the same crash consequence.
* No Confidentiality or Integrity points are awarded merely from the generic exploitation potential of a UAF.
* NEW52 B5-R does not apply. There is no retry-accumulated heap OOB write.
* NEW53 B3-PENDING does not apply. There is no demonstrated write to shared file-backed storage.
* V33 does not apply on the supplied evidence. A stale active pointer and privileged kernel consumer exist, but a concrete guest, namespace, or delegated-interface attacker boundary is not established.
* No concrete repeated release or refcount operation exists. The patch does not show an initial lifetime-ending put followed by another put on the exact dangling reference. The dedicated plus one was not awarded, paranoid refcount leverage was withheld, and FLOOR 5 was not applied.

3. Reachability analysis

The vulnerable operation is in the Open vSwitch conntrack data path. Reproduction requires an skb with a shared unconfirmed conntrack entry, at least two clones committing that entry with different extension sets, failure of the first confirmation, and later destruction through the stale expectation pointer.

Creating the required Open vSwitch flow topology normally involves control-plane configuration, but the supplied material does not establish whether host CAP_NET_ADMIN, namespace-scoped CAP_NET_ADMIN, a delegated OVS controller, or an already configured pipeline is sufficient for the complete sequence. Therefore HostAdminRequired and NamespaceScopedPrivilege remain UNKNOWN.

A packet sender might exercise an already configured vulnerable pipeline without local privileges, but no practical such pipeline or complete packet-only trigger is demonstrated. Prior privileged setup is plausible but not conclusively established as mandatory. No special hardware or boot option is involved. The ordering appears repeatable in principle, but attacker control over both commit paths and the confirmation failure remains unresolved.

4. Primitive and severity interpretation

The exact primitive is a stale pointer into conntrack extension storage. Modification of a shared unconfirmed conntrack entry can invalidate an extension pointer previously inserted into an expectation list. The stale pointer is later used on the destruction path, establishing a real UAF.

This is an active structured conntrack object rather than fixed stale DMA storage. However, the demonstrated stale use is destruction-oriented and no useful operation beyond a potential fault is established. There is no concrete second release or refcount mutation through the stale pointer.

The issue is therefore CLASS_B rather than CLASS_A. The demonstrated consequence is kernel crash or denial of service. Controlled reclaim, arbitrary kernel read or write, callback influence, information disclosure, and privilege escalation remain speculative.

ImportantCandidate is NO because the supplied evidence does not establish meaningful exploitation leverage beyond the constrained destruction-path UAF. Manual review is still recommended because the bug is a genuine kernel lifetime violation and packet-driven reachability has not been conclusively excluded. AutoDowngradeAllowed is YES because no unresolved controlled corruption or credible cross-boundary primitive is established.

5. One-sentence report phrase

A shared unconfirmed Open vSwitch conntrack entry can have its extension storage replaced while an expectation retains a stale pointer, causing a destruction-path use after free and potential kernel crash, although a practical below-host-admin packet-only trigger is not established.

6. Manual review recommendation

MANUAL CHECK RECOMMENDED

The UAF is concrete, but practical pipeline reachability, attacker privilege, namespace scope, and exploitation leverage beyond DoS remain unresolved.

7. Call-site confidence

Call-site confidence: medium

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UPSTREAM PATCH SUMMARY
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Patch: net: openvswitch: conntrack: avoid modifying shared unconfirmed ct entry
Commit: e0fa5ea434b7e8467ef3adc64e3858b1ca2a642d
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=e0fa5ea434b7e8467ef3adc64e3858b1ca2a642d

Commit description:

In a case where skb with an unconfirmed ct entry gets cloned, we may
end up committing both but with different sets of extensions.

The series of events:

 1. The first clone wants to commit and runs the helpers wiring up
    the extension pointer into the expectation list.
 2. Then it looses the confirmation keeping the entry unconfirmed.
 3. Second clone now wants to commit labels and adds the new extension
    for that breaking the pointer in the expectation list causing
    UAF on the destruction path later.

While this is possible to trigger, there should be no practical
network pipeline where committing both clones without modifications
into the same zone is needed.  So, let's just reset the entry in case
for some reason we got an skb with a shared one during commit.  This
doesn't affect any known use cases, but avoids any potential problems
with sharing and modification of the unconfirmed ct entry.

The fixes tag points to the introduction of helpers, since that's the
main UAF trigger for the sharing.

Fixes: cae3a26 ("openvswitch: Allow attaching helpers to ct action")
Cc: stable@vger.kernel.org
Reported-by: Axel Mierczuk <axel.mierczuk@1password.com>
Signed-off-by: Ilya Maximets <i.maximets@ovn.org>
Reviewed-by: Aaron Conole <aconole@redhat.com>
Link: https://patch.msgid.link/20260921145655.3167436-2-i.maximets@ovn.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  include/net/netfilter/nf_conntrack.h
  net/openvswitch/conntrack.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=e0fa5ea434b7e8467ef3adc64e3858b1ca2a642d

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

The original Linux kernel CVE announcement for CVE-2026-98491 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98491

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:L/I:L/A:H
  The Best / paranoid CVSS vector: AV:A/AC:H/PR:N/UI:N/S:U/C:H/I:H/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: unknown
  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: YES
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).