[CVE-2026-90077][LOW] net: fix a resource leak in copy_net_ns() error handling path [ Upstream

[CVE-2026-90077][LOW] net: fix a resource leak in copy_net_ns() error handling path [ Upstream

[AL-KERNEL]

CVE: CVE-2026-90077
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: net: fix a resource leak in copy_net_ns() error handling path [ Upstream
Commit: 76c847e80d2b6be047707d58e8e05eedbe2593ad
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=76c847e80d2b6be047707d58e8e05eedbe2593ad
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90077
Analysis date: Fri, 18 Sep 2026 01:40:28 -0400
ActionableScore: 2
ActionableScore lower bound: 1
Actionable bucket: Ordinary Moderate
Manual review required: NO

Summary:
No one-sentence report phrase was found.

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

The original Linux kernel CVE announcement for CVE-2026-90077 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90077

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.

======================================================================
AL-KERNEL CLASSIFICATION RESULT
======================================================================

CVE-2026-90077	LOW	https://www.kernelcve.org/list/?q=CVE-2026-90077 CHECK WITH IMPACT FROM ORIG NN LOW	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H';*CWE-401;*CWE-772;CWE-404;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '4.7';DESCR 'A resource leak in copy_net_ns() occurs when ns_common_init() fails after net_alloc() has allocated and initialized part of a network namespace. The error path skips key_remove_domain() and net_passive_dec(), leaving references and associated resources unreleased. A local process must be able to create network namespaces and must also cause ns_common_init() to fail, so reliable triggering normally depends on resource pressure or identifier exhaustion. For the CVSS the PR:L is selected because an unprivileged local user may create a user namespace and then obtain the capability needed to create a network namespace when unprivileged user namespaces are enabled. The issue is not network reachable because incoming traffic does not invoke the namespace creation error path. Impact is limited to resource consumption and potential local denial of service after sustained abuse. No memory corruption, information disclosure, or privilege escalation primitive is supported by the affected control flow.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 2)  SKIP CVE-2026-90077 UNKNOWN SKIP The Fixes patch not applied yet, so unlikely that actual: url YES  NO NO unknown 	MAYBE	REMOTE INIT SIMPLEFIX LEAK ERRORPATH 	-	-	checked

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

ActionableScore=2
ActionableScoreLower=1
PrimitiveClass=CLASS_C
RealUAF=NO
HostAdminRequired=UNKNOWN
NamespaceScopedPrivilege=UNKNOWN
ImportantCandidate=NO
ManualReview=NO
AutoDowngradeAllowed=YES

1. ActionableScore

* Raw conservative score: 1
* Conservative score: 1
* Raw paranoid score: 2
* Paranoid score: 2
* No floor or cap was applied.
* Final recommended bucket: **Ordinary Moderate**::

2. Signal breakdown

Conservative signals:

* +1 Concrete persistent kernel resource/reference leak. If `ns_common_init()` fails, the old error path bypasses `key_remove_domain()` and `net_passive_dec()`, permanently losing resources allocated by `net_alloc()`.
* No negative privilege penalty. Host-admin-equivalent privilege is not positively established, but complete below-host-admin reachability is configuration-dependent and also not established.

Additional paranoid signal:

* +1 Resource exhaustion potential. Repeated namespace-creation failures can accumulate leaked network-namespace resources and plausibly increase host memory or reference pressure.

Not awarded:

* No UAF, double release, OOB access, stale dereference, or memory-corruption primitive.
* No reliable immediate kernel crash is demonstrated.
* No C/I, authorization bypass, namespace-isolation bypass, or privilege-escalation signal.
* No remote reachability. Network traffic does not invoke `copy_net_ns()`.
* No local-unprivileged bonus because unprivileged user-namespace availability and the complete trigger conditions are not established for the evaluated system.
* No race or timing penalty. This is a deterministic error-path cleanup defect.
* No additional availability point because host-wide exhaustion requires sustained failure and repetition rather than a single operation.

3. Reachability analysis

The trigger is local and requires creation of a network namespace followed by failure of `ns_common_init()`. A host administrator can reach namespace creation, while an ordinary user may reach it on systems that permit unprivileged user namespaces and allow creation of the associated network namespace.

The complete below-host-admin path is not established for all deployments, so `HostAdminRequired` and `NamespaceScopedPrivilege` remain `UNKNOWN`. Enabling unprivileged user namespaces may constitute prior administrator-controlled setup on restricted systems. No network exposure, special hardware, race, boot mode, or device prerequisite is involved. Repetition is inexpensive only after the attacker can both create network namespaces and reliably induce the initialization failure.

4. Primitive and severity interpretation

The exact primitive is a persistent resource and reference leak on an initialization error path. It is not a post-lifetime access. The patch does not establish a dangling pointer, second lifetime mutation, active structured-object UAF, or controlled corruption.

The demonstrated consequence is leaked kernel resources. Sustained repetition could plausibly cause resource exhaustion, but immediate host-wide failure is not demonstrated. There is no supported path to confidentiality loss, integrity modification, or privilege escalation.

This is `CLASS_C` because the security-relevant behavior is limited to potential resource-exhaustion DoS. `ImportantCandidate=NO` because no corruption, ownership-boundary, or authorization primitive exists. `AutoDowngradeAllowed=YES` because the issue is a bounded error-path resource leak without unresolved exploitation leverage. Likely operational severity is Low to ordinary Moderate.

5. One-sentence report phrase

A failed network namespace initialization can bypass required cleanup and leak kernel resources, potentially causing local resource exhaustion after sustained repetition.

6. Manual review recommendation

NO MANUAL CHECK NEEDED

The patch establishes only a resource leak with no memory corruption, security-boundary bypass, or Important-grade exploitation primitive.

7. Call-site confidence

Call-site confidence: high

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

Patch: net: fix a resource leak in copy_net_ns() error handling path [ Upstream
Commit: 76c847e80d2b6be047707d58e8e05eedbe2593ad
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=76c847e80d2b6be047707d58e8e05eedbe2593ad

Changed files:
  net/core/net_namespace.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=76c847e80d2b6be047707d58e8e05eedbe2593ad

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

The original Linux kernel CVE announcement for CVE-2026-90077 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90077

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:N/I:N/A:L
  The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS score: 4.7

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: 1
  Paranoid ActionableScore: 2

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).