[CVE-2026-74718][LOW] devlink: fix net namespace reference leak in reload [ Upstream

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

CVE: CVE-2026-74718
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: devlink: fix net namespace reference leak in reload [ Upstream
Commit: 7b6552e53426ea0539c667bbc5a524fdf7feae6f
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=7b6552e53426ea0539c667bbc5a524fdf7feae6f
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74718
Analysis date: Sat, 22 Aug 2026 13:14:29 -0400
ActionableScore: 1
ActionableScore lower bound: 0
Actionable bucket: Ordinary Moderate / Low-like
Manual review required: NO

Summary:
A missing `put_net()` in the devlink reload error path can leak net namespace references when namespace change is rejected for non DRIVER_REINIT reload actions, causing possible resource exhaustion after repeated privileged local triggering.

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

The original Linux kernel CVE announcement for CVE-2026-74718 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74718

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
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CVE-2026-74718	LOW	CHECK WITH IMPACT FROM ORIG NN LOW	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H';*CWE-772;*CWE-401;CWE-404;**CWE-400;Other CVSS 'AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '4.4';DESCR 'devlink reload can leak a net namespace reference on an error path because devlink_nl_reload_doit gets a referenced destination net namespace and returns EOPNOTSUPP without dropping it when namespace change is requested for a non DRIVER_REINIT action. Repeated triggering can keep deleted net namespaces alive and may cause resource exhaustion over time, but the primitive is a reference leak rather than memory corruption. For the CVSS the PR:H is used because reliable triggering normally requires administrative devlink control such as CAP_NET_ADMIN and access to a devlink device. The issue is not directly network reachable and is triggered through local generic netlink control plane operations. Impact is denial of service through resource leakage only, with no supported confidentiality or integrity impact.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like (with actual score 1)	YES	SIMPLEFIX LEAK ERRORPATH 	YES	NO	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=1
ActionableScoreLower=0

## 1. ActionableScore

* Conservative score: 0
* Paranoid score: 1
* Final recommended bucket: **Ordinary Moderate / Low-like**

## 2. Signal breakdown

Triggered signals:

* Availability impact realistic: +1
  Repeated triggering can leak references to destination net namespaces and keep them alive longer than intended, which may cause gradual resource exhaustion.

Subtracted signals:

* Requires admin/root/CAP_NET_ADMIN in typical deployments: -2
  The affected path is devlink reload via generic netlink and normally requires administrative network or device-management privileges plus access to a devlink-capable device.

Not triggered:

* Remote reachable / network-triggerable: +0
  This is a local control-plane devlink operation, not packet-triggered.
* Local unprivileged trigger: +0
  No evidence that an unprivileged local user can reliably reach this path in typical deployments.
* Generic memory corruption: +0
  The bug is a missing put_net() reference release, not UAF, double free, OOB write, type confusion, or arbitrary write.
* Privilege escalation plausible: +0
  No plausible LPE primitive is supported by the patch.
* Strong DoS: +0
  The impact is gradual reference/resource leakage, not an immediate reliable kernel crash or system-wide failure.

## 3. Reachability analysis

The bug is reachable through `devlink_nl_reload_doit()` when a requested destination network namespace differs from the current one and the reload action is not `DEVLINK_RELOAD_ACTION_DRIVER_REINIT`. In that error path, `devlink_netns_get()` returns a referenced `struct net`, but the old code returned `-EOPNOTSUPP` without calling `put_net()`.

Reliable triggering normally requires CAP_NET_ADMIN or equivalent administrative control over devlink plus a devlink-capable device. Namespace or container delegation could reduce practical privilege requirements in unusual deployments, but this is not a default unprivileged interface. The path is not network-triggerable by packet traffic.

## 4. Severity interpretation

This behaves like a Low-like or ordinary Moderate resource leak, not an Important-class vulnerability. The realistic impact is denial of service through gradual accumulation of leaked net namespace references if an already privileged actor repeatedly triggers the error path. There is no demonstrated memory corruption, no confidentiality impact, no integrity impact, and no practical privilege-escalation path.

Theoretical worst case is resource exhaustion over time, but the required privileges and lack of a corruption primitive make this suitable for low-priority handling.

## 5. One-sentence report phrase

A missing `put_net()` in the devlink reload error path can leak net namespace references when namespace change is rejected for non DRIVER_REINIT reload actions, causing possible resource exhaustion after repeated privileged local triggering.

## 6. Manual review recommendation

NO MANUAL CHECK NEEDED

This is a straightforward reference leak on an administrative devlink error path. It has no supported memory corruption or privilege-escalation primitive and can be handled as low-priority unless the product delegates devlink control to untrusted users.

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

Patch: devlink: fix net namespace reference leak in reload [ Upstream
Commit: 7b6552e53426ea0539c667bbc5a524fdf7feae6f
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=7b6552e53426ea0539c667bbc5a524fdf7feae6f

Changed files:
  net/devlink/dev.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=7b6552e53426ea0539c667bbc5a524fdf7feae6f

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

The original Linux kernel CVE announcement for CVE-2026-74718 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74718

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:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS score: 4.4

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: 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).