[CVE-2026-46165][LOW] openvswitch: vport: fix self-deadlock on release of tunnel ports

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

CVE: CVE-2026-46165
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: openvswitch: vport: fix self-deadlock on release of tunnel ports
Commit: c741433f6c8dcdecd1d9549d89053761fd1ea413
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=c741433f6c8dcdecd1d9549d89053761fd1ea413
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46165
Analysis date: Thu, 28 May 2026 11:26:55 -0400
ActionableScore: 1
ActionableScore lower bound: unknown
Actionable bucket: Ordinary Moderate / Low-like
Manual review required: NO

Summary:
Open vSwitch tunnel vport deletion could self-deadlock by queuing the RCU release after `rtnl_unlock()` waits for netdev references, causing an availability-only control-plane hang.

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

The original Linux kernel CVE announcement for CVE-2026-46165 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46165

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: LOW
Manual review required: NO

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
======================================================================

CVE-2026-46165	LOW	CHECK	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H';CWE-667;*CWE-833;**CWE-400;Other CVSS 'AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '5.5';DESCR 'Open vSwitch tunnel vport removal could self-deadlock because rtnl_unlock can run netdev_run_todo and wait for netdev references before the RCU callback that releases the vport reference was queued. A user who can manage OVS tunnel ports can trigger the hang during tunnel vport deletion. For the CVSS the PR:L is used only for the paranoid score when reduced privilege users, container root, or delegated CAP_NET_ADMIN can manage OVS networking. The issue is not network reachable by packets and is triggered through local control plane operations. Impact is availability only through a stuck device removal or OVS networking control plane hang, with no supported memory corruption, information disclosure, or privilege escalation primitive.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like (with actual score 1)  SKIP CVE-2026-46165  SKIP The Fixes patch not applied yet, so unlikely that actual: 6931d21f87bc6d657f145798fad0bf077b82486c YES  NO NO unknown 	MAYBE	DEADLOCK DANGER UAF HARDWARE  DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS_AND_CIANNH DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3	-	-	checked

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

ActionableScore=1

## 1. ActionableScore

* Conservative score: 1
* Paranoid score: 1
* Final recommended bucket: **Ordinary Moderate / Low-like**::

## 2. Signal breakdown

Positive signals:

* Availability impact realistic: +1. Tunnel vport deletion can self-deadlock and hang device removal or the OVS networking control plane.

Limiting factors:

* Requires admin/CAP_NET_ADMIN in typical deployments: -2. Creating or deleting OVS tunnel ports normally requires administrative network control.
* No remote packet trigger. The issue is reached through local OVS control-plane operations.
* No memory corruption.
* No information disclosure.
* No privilege escalation.
* No strong cross-boundary bypass is shown. Delegated container networking may make this operationally relevant, but the primitive remains DoS-only.

Effective score is kept at 1 rather than negative because a control-plane deadlock can still be operationally significant.

## 3. Reachability analysis

A user who can manage Open vSwitch tunnel ports can trigger the issue by deleting a tunnel vport. In normal deployments this requires root, OVS administrative rights, or `CAP_NET_ADMIN`.

Namespaces and containers matter if tenants are delegated OVS or network administration. In that case, the bug may allow a reduced-privilege network administrator to hang part of the networking control plane, but it does not bypass an additional security boundary by itself.

The path is not reachable by network packets alone.

## 4. Severity interpretation

This behaves like Low / ordinary Moderate from a security perspective. The realistic impact is an availability-only local control-plane hang.

It does not behave like an Important vulnerability because there is no memory corruption, no data exposure, no LPE path, and no remote packet-triggered attack.

## 5. One-sentence report phrase

Open vSwitch tunnel vport deletion could self-deadlock by queuing the RCU release after `rtnl_unlock()` waits for netdev references, causing an availability-only control-plane hang.

## 6. Manual review recommendation

NO MANUAL CHECK NEEDED

This can generally be auto-closed for security triage unless untrusted tenants can manage OVS tunnel ports. The supported impact is privileged local DoS only.

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

Patch: openvswitch: vport: fix self-deadlock on release of tunnel ports
Commit: c741433f6c8dcdecd1d9549d89053761fd1ea413
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=c741433f6c8dcdecd1d9549d89053761fd1ea413

Commit description:

vports are used concurrently and protected by RCU, so netdev_put()
must happen after the RCU grace period.  So, either in an RCU call or
after the synchronize_net().  The rtnl_delete_link() must happen under
RTNL and so can't be executed in RCU context.  Calling synchronize_net()
while holding RTNL is not a good idea for performance and system
stability under load in general, so calling netdev_put() in RCU call
is the right solution here.

However,
when the device is deleted, rtnl_unlock() will call netdev_run_todo()
and block until all the references are gone.  In the current code this
means that we never reach the call_rcu() and the vport is never freed
and the reference is never released, causing a self-deadlock on device
removal.

Fix that by moving the rcu_call() before the rtnl_unlock(), so the
scheduled RCU callback will be executed when synchronize_net() is
called from the rtnl_unlock()->netdev_run_todo() while the RTNL itself
is already released.

Fixes: 6931d21 ("openvswitch: defer tunnel netdev_put to RCU release")
Cc: stable@vger.kernel.org
Acked-by: Eelco Chaudron <echaudro@redhat.com>
Signed-off-by: Ilya Maximets <i.maximets@ovn.org>
Acked-by: Aaron Conole <aconole@redhat.com>
Link: https://patch.msgid.link/20260430233848.440994-2-i.maximets@ovn.org
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  net/openvswitch/vport-netdev.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=c741433f6c8dcdecd1d9549d89053761fd1ea413

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

The original Linux kernel CVE announcement for CVE-2026-46165 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46165

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:H
  The Best / paranoid CVSS vector: AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS score: 5.5

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: 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: LOW
KPANIC detected for this report: NO
Published priority for this report (same as in Subject): LOW

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).