[CVE-2026-89488][IMPORTANT] openvswitch: Fix CT limit teardown use-after-free [ Upstream

[CVE-2026-89488][IMPORTANT] openvswitch: Fix CT limit teardown use-after-free [ Upstream

[AL-KERNEL]

CVE: CVE-2026-89488
Priority: IMPORTANT
AL-KERNEL base severity: IMPORTANT
KPANIC flag: YES
Patch: openvswitch: Fix CT limit teardown use-after-free [ Upstream
Commit: e15407c3a8a005324f633cd46cd8fb58042c1157
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=e15407c3a8a005324f633cd46cd8fb58042c1157
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-89488
Analysis date: Fri, 11 Sep 2026 20:02:27 -0400
ActionableScore: 6
ActionableScore lower bound: 5
Actionable bucket: Actionable Moderate / Strong Important candidate requiring manual review
Manual review required: YES

Summary:
No one-sentence report phrase was found.

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

The original Linux kernel CVE announcement for CVE-2026-89488 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-89488

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: IMPORTANT
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-2026-89488	IMPORTANT	https://www.kernelcve.org/list/?q=CVE-2026-89488 CHECK WITH IMPACT FROM ORIG NN IMPORTANT	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H';*CWE-416;CWE-362;*CWE-664;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:H';BEST CVSS score: '7';DESCR 'Open vSwitch CT limit state can be freed during network namespace teardown while packet processing still reads the same pointer under RCU, creating a slab use-after-free in ovs_ct_execute. An unprivileged local user can trigger this from a user and network namespace when Open vSwitch conntrack zone limits are available, by arranging packet processing and namespace teardown to overlap. For the CVSS the PR:L is used because reliable triggering requires local code execution or a local process context, but not full host administrator privileges when unprivileged user namespaces provide CAP_NET_ADMIN inside the created namespace. The issue is not directly network reachable from a remote only attacker because teardown of the relevant network namespace is part of the trigger. Impact is at least local denial of service via kernel crash, and in the paranoid case may include confidentiality and integrity impact because this is an explicit use-after-free in kernel packet processing state.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate / Strong Important candidate requiring manual review (with actual score 6)	YES	OOB LOCK INIT UAF IMPROVEONLY LINUS KPANIC PACKET 	NO	NO	checked

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

ActionableScore=6
ActionableScoreLower=5
PrimitiveClass=CLASS_B
RealUAF=YES
HostAdminRequired=NO
NamespaceScopedPrivilege=YES
ImportantCandidate=YES
ManualReview=REQUIRED
AutoDowngradeAllowed=NO

1. ActionableScore

* Raw conservative score: 5
* Conservative score: 5
* Raw paranoid score: 6
* Paranoid score: 6
* Final recommended bucket: **Actionable Moderate / Strong Important candidate requiring manual review**::

No floor or cap changed the score.

2. Signal breakdown

Positive signals:

* +2 Real UAF / active lifetime violation: CT limit state is freed during netns teardown while packet processing can still dereference it under RCU in ovs_ct_execute().
* +1 Local unprivileged trigger: supplied context explicitly states that an unprivileged user can trigger the bug from a user and network namespace.
* +1 Reliable kernel crash / strong DoS: the established consequence is slab-use-after-free in packet processing, realistically leading to kernel crash or fatal KASAN/Oops.
* +1 Concrete RCU referenced-object lifetime mismatch: ovs_net remains visible while its ct_limit_info referenced object can be freed before readers finish. The fix detaches the pointer and relies on the pernet RCU grace period before freeing.
* Paranoid +1 Structured stale-object exploitation leverage: the stale object is active packet-processing state, not a fixed stale buffer, and stale use can traverse CT limit structures and conncount state. This is unresolved exploitation surface beyond a trivial NULL dereference, but not enough for CLASS_A.

Non-awarded signals:

* +2 strong exploitation leverage not awarded: no controlled reclaim, arbitrary write, callback control, refcount takeover, or demonstrated LPE is shown.
* Remote reachable +2 not awarded: a remote-only attacker cannot trigger netns teardown.
* Extra availability +1 not awarded: the crash/DoS is already counted once.
* Confidentiality and integrity bonuses not awarded conservatively: C/I are not demonstrated by an information leak, arbitrary write, or protected object corruption.
* Race/timing penalty not applied: the bug is a race, but the supplied context says an unprivileged user can trigger it, and repeated namespace setup/teardown attempts are plausible.
* Concrete repeated release/refcount +1 not awarded: the patch shows free-after-RCU lifetime mismatch, not a second put/release/refcount mutation on the same dangling reference.

Repeated release/refcount checklist:

* First release can end lifetime: yes, teardown frees CT limit state.
* Exact same reference survives: readers may still observe the old pointer through RCU.
* Second operation is real lifetime/refcount mutation: no, stale path dereferences/uses state rather than performing a second put/refcount mutation.
* Concrete repeated release/refcount +1 awarded: no.
* Paranoid repeated-refcount leverage +1 awarded: no.
* FLOOR 5 applied: no explicit floor needed because raw conservative score is already 5.

3. Reachability analysis

The supplied context positively establishes below-host-admin reachability: an unprivileged local user can trigger the issue from a user and network namespace. Therefore HostAdminRequired=NO.

NamespaceScopedPrivilege=YES because the input specifically ties the complete trigger to attacker-created user and network namespaces rather than merely mentioning netns cleanup. The attacker model is local unprivileged namespace-based execution, not host administrator.

The issue is not directly network reachable from a remote-only attacker. Packet traffic participates in the vulnerable data path, but teardown of the relevant network namespace is part of the trigger and requires local namespace control.

Prior host setup is partially configuration dependent: Open vSwitch and conntrack zone limit support must be available, and CONFIG_NETFILTER_CONNCOUNT is relevant. This does not justify a rare-subsystem penalty because the supplied evidence establishes an unprivileged namespace trigger when the feature is present.

No special hardware requirement is present. Race repeatability appears meaningful because the attacker can drive packet processing and namespace teardown attempts, so no hard-race penalty is applied.

4. Primitive and severity interpretation

The exact primitive is an RCU lifetime violation causing slab-use-after-free: ct_limit_info is freed during netns teardown while concurrent packet processing can still read it.

This is an active structured object, not fixed stale storage. The stale CT limit state is used in packet-processing logic, including limit lookup and conncount-related state, rather than only being passed to a shallow cleanup destructor.

This is CLASS_B because a real kernel lifetime/corruption primitive is established, but no controlled reclaim, arbitrary read/write, function-pointer control, or demonstrated privilege escalation is established.

Demonstrated consequence is local DoS through kernel crash or fatal use-after-free. Speculative consequence is possible broader C/I impact if post-free reuse can be made useful, but that is not demonstrated strongly enough for CLASS_A or score 7.

ImportantCandidate=YES because this is a below-host-admin active-object UAF in packet processing with unresolved exploitation leverage. AutoDowngradeAllowed=NO because automatic closure would discard a concrete UAF with meaningful active-state RCU lifetime mismatch and namespace-based reachability.

Likely operational severity is actionable Moderate at minimum, with Strong Important review warranted if further analysis shows controlled reuse, useful stale field consumption, or privilege escalation potential.

5. One-sentence report phrase

Open vSwitch CT limit teardown can free RCU-read packet-processing state while ovs_ct_execute still uses it, allowing a local unprivileged namespace user to trigger a slab-use-after-free and kernel DoS with unresolved exploitation leverage requiring manual review.

6. Manual review recommendation

MANUAL CHECK REQUIRED

Reason: explicit UAF, below-host-admin namespace trigger, active packet-processing state, and unresolved post-free exploitation leverage.

7. Call-site confidence

Call-site confidence: high

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

Patch: openvswitch: Fix CT limit teardown use-after-free [ Upstream
Commit: e15407c3a8a005324f633cd46cd8fb58042c1157
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=e15407c3a8a005324f633cd46cd8fb58042c1157

Changed files:
  net/openvswitch/conntrack.c
  net/openvswitch/conntrack.h
  net/openvswitch/datapath.c
  net/openvswitch/datapath.h

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=e15407c3a8a005324f633cd46cd8fb58042c1157

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

The original Linux kernel CVE announcement for CVE-2026-89488 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-89488

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:L/UI:N/S:U/C:L/I:L/A:H
  The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
  The Best / paranoid CVSS score: 7

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: 5
  Paranoid ActionableScore: 6

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: IMPORTANT
KPANIC detected for this report: YES
Published priority for this report (same as in Subject): IMPORTANT

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).