[CVE-2026-74464][MODERATE REGULAR] net: openvswitch: fix skb leak on flow key update failure during ct

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

CVE: CVE-2026-74464
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: net: openvswitch: fix skb leak on flow key update failure during ct
Commit: 736e972f3f8a304158345223ac6e816166a467ce
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=736e972f3f8a304158345223ac6e816166a467ce
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74464
Analysis date: Sat, 15 Aug 2026 14:56:01 -0400
ActionableScore: 4
ActionableScore lower bound: 1
Actionable bucket: Borderline, manual review recommended
Manual review required: YES

Summary:
Open vSwitch may leak an skb when ovs_flow_key_update fails before conntrack execution, and repeated packet-triggered hits against a suitable preconfigured OVS action pipeline could cause resource-exhaustion DoS.

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ABOUT THIS REPORT
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The original Linux kernel CVE announcement for CVE-2026-74464 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74464

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: 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-2026-74464	MODERATE	CHECK WITH IMPACT FROM ORIG NN LOW	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-401;*CWE-772;**CWE-400;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '5.3';DESCR 'Open vSwitch can leak an skb when ovs_flow_key_update fails while refreshing an invalid flow key before ct execution. The failure path returned immediately even though ovs_flow_key_update does not consume or free the skb, so the common cleanup path was skipped. For the CVSS the PR:N is used in the paranoid network-adjacent scenario because if a vulnerable OVS action pipeline already exists, an attacker may only need packet reachability to trigger repeated leaks. The realistic base case is more restricted because reliable construction of the required action pipeline usually needs CAP_NET_ADMIN or equivalent OVS control. The issue is hard to trigger because the packet must become unparseable after actions were applied to a previously parseable skb. Impact is denial of service via resource exhaustion only, with no evidence of UAF, out of bounds access, information disclosure, or privilege escalation.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline, manual review recommended (with actual score 3)	YES	SIMPLEFIX LEAK ERRORPATH SKB IMPROVEONLY LINUS PACKET  INCREASED_TO_MODERATE_FROM_LOW_BASED_ON_GUESSCVSS DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS_AND_CIANNH	NO	NO	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=4
ActionableScoreLower=1

## 1. ActionableScore

* Conservative score: 1
* Paranoid score: 4
* Final recommended bucket: **Borderline, manual review recommended**

## 2. Signal breakdown

Paranoid score signals:

* Remote reachable / network-triggerable: +2
  If an affected Open vSwitch datapath and action pipeline already exist, an attacker with packet reachability may be able to trigger the leak by sending traffic through that pipeline.

* Reliable kernel crash / strong DoS: +1
  The bug is an skb leak. Repeated triggering could cause resource exhaustion, but this is not an immediate crash primitive.

* Common networking packet-processing path: +1
  Open vSwitch is a packet-processing datapath used in virtualization and cloud networking environments.

* Hard or unreliable trigger: -1
  The commit explicitly says the scenario is very unlikely and requires a packet to become unparseable after actions are applied to a previously parseable skb.

* Availability impact realistic: +1
  Sustained skb leaks can plausibly create availability impact through memory or networking resource exhaustion.

Conservative score signals:

* Availability impact realistic: +1
  The direct impact is resource leakage.

* Requires admin/root/CAP_NET_ADMIN in typical deployments: -2
  Creating the needed OVS action pipeline normally requires privileged OVS or network administration control.

* Hard or unreliable trigger: -1
  The failure condition is described as very unlikely.

* Common networking packet-processing path: +1
  OVS is relevant in common virtual networking deployments.

Conservative total is effectively low, rounded to 1 for practical triage rather than negative.

## 3. Reachability analysis

In the conservative model, reliable triggering requires control over Open vSwitch flows/actions, which normally means CAP_NET_ADMIN or equivalent OVS administrative access. In that case this is mostly a privileged local or management-plane resource leak.

In the paranoid model, if a vulnerable OVS pipeline is already configured by an administrator, an external or adjacent network sender may only need packet reachability to repeatedly hit the affected datapath. This is not a generic Internet-remote kernel bug, but it can be network-adjacent in virtualized or cloud networking deployments.

Namespaces and containers matter because OVS control may be delegated in some environments. However, ordinary unprivileged local users typically cannot configure the required datapath.

## 4. Severity interpretation

This behaves more like a borderline actionable Moderate than an Important-class vulnerability. The patch shows an skb ownership/cleanup bug causing a leak, not UAF, OOB access, double-free, type confusion, arbitrary write, or privilege escalation.

The realistic impact is DoS by resource exhaustion under a rare error path. The main reason not to auto-close immediately is the packet-triggered paranoid scenario in OVS deployments where untrusted traffic can reach a preconfigured vulnerable pipeline.

## 5. One-sentence report phrase

Open vSwitch may leak an skb when ovs_flow_key_update fails before conntrack execution, and repeated packet-triggered hits against a suitable preconfigured OVS action pipeline could cause resource-exhaustion DoS.

## 6. Manual review recommendation

MANUAL CHECK RECOMMENDED

Reason: this is DoS-only resource leakage with no memory corruption or LPE evidence, but the network-adjacent OVS datapath scenario makes it worth checking deployment exposure before auto-closing.

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

Patch: net: openvswitch: fix skb leak on flow key update failure during ct
Commit: 736e972f3f8a304158345223ac6e816166a467ce
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=736e972f3f8a304158345223ac6e816166a467ce

Commit description:

ovs_ct_execute() always steals or frees the skb on failure while
ovs_flow_key_update() does not.  So, if it fails and we return right
away, the skb ends up leaked.

Fix that by breaking instead and letting the common error handling
code at the bottom of the loop to free the skb properly.

This is a very unlikely scenario as it requires the packet to become
unparseable by applying a set of actions on a previously parseable skb,
but should be fixed nevertheless.

Reported by Sashiko.

Fixes: ec0d043 ("openvswitch: Ensure flow is valid before executing ct")
Cc: stable@vger.kernel.org
Signed-off-by: Ilya Maximets <i.maximets@ovn.org>
Reviewed-by: Aaron Conole <aconole@redhat.com>
Link: https://patch.msgid.link/20260727181851.306076-3-i.maximets@ovn.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  net/openvswitch/actions.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=736e972f3f8a304158345223ac6e816166a467ce

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

The original Linux kernel CVE announcement for CVE-2026-74464 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74464

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: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: 1
  Paranoid ActionableScore: 4

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).