[CVE-2026-53238][MODERATE REGULAR] netlabel: validate unlabeled address and mask attribute lengths [ Upstream

[CVE-2026-53238][MODERATE REGULAR] netlabel: validate unlabeled address and mask attribute lengths [ Upstream

[AL-KERNEL]

CVE: CVE-2026-53238
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: netlabel: validate unlabeled address and mask attribute lengths [ Upstream
Commit: 975a84fd741440853380d37465b6e226cf47254c
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=975a84fd741440853380d37465b6e226cf47254c
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53238
Analysis date: Thu, 25 Jun 2026 07:29:27 -0400
ActionableScore: 4
ActionableScore lower bound: 2
Actionable bucket: Borderline manual review recommended / not Strong Important by default
Manual review required: YES

Summary:
A crafted local NetLabel Generic Netlink request can provide a valid IPv4 or IPv6 address with a short mask attribute, causing the kernel to read the mask as a full address-sized structure and potentially affecting NetLabel policy handling or stability.

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

The original Linux kernel CVE announcement for CVE-2026-53238 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53238

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-2026-53238	MODERATE	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:L/I:L/A:H';CWE-125;*CWE-20;CWE-130;Other CVSS 'AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:L/A:L';BEST CVSS score: '6.6';DESCR 'NetLabel unlabeled address parsing used Generic Netlink binary attributes where the policy length was only a maximum length, not an exact length. A crafted local Generic Netlink request could provide a valid IPv4 or IPv6 address attribute together with a shorter mask attribute, and later code may read that mask as a full struct in_addr or struct in6_addr. This is an out of bounds read risk in the NetLabel configuration path. For the CVSS the PR:L is used in the paranoid score because some deployments may delegate network administration or NetLabel configuration through CAP_NET_ADMIN to a service account or container context, even though the typical base case is administrative PR:H. The issue is not directly network reachable and is triggered through local control plane Netlink configuration, not by remote packets. Impact is at least policy integrity risk and possible denial of service. In the worst still defensible case it may allow limited confidentiality or integrity impact due to adjacent attribute data being read as mask data, but there is no clear arbitrary write primitive.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline manual review recommended / not Strong Important by default (with actual score 3)	YES	OOB SIMPLEFIX LINUS IPV6  DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5	NO	NO	checked

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

ActionableScore=4
ActionableScoreLower=2

## 1. ActionableScore

* Conservative score: 2
* Paranoid score: 4
* Final recommended bucket: **Borderline manual review recommended / not Strong Important by default**::

## 2. Signal breakdown

Conservative signals:

* Weak/indirect corruption candidate: +1. A crafted Generic Netlink request can provide a short mask attribute that is later read as a full `struct in_addr` or `struct in6_addr`, creating a limited OOB read / invalid struct interpretation risk.
* Integrity impact plausible: +1. The mask is used in NetLabel security policy configuration, so misreading mask data could affect labeling policy semantics.
* Availability impact possible: +1. An OOB read in kernel parsing code may produce warnings or crashes in some builds or layouts, but the patch does not show a reliable panic primitive.
* Requires CAP_NET_ADMIN in typical deployments: -1 to -2. Conservative score treats this as privileged local control-plane access, reducing practical exposure.

Paranoid signals:

* Weak/indirect corruption candidate: +1.
* Integrity impact plausible: +1.
* Availability impact plausible: +1.
* Cross-boundary / policy bypass concern: +1. NetLabel is security-labeling infrastructure, so malformed policy input deserves manual review even without a write primitive.
* CAP_NET_ADMIN penalty reduced in paranoid view. Some deployments may delegate network administration to containers, service accounts, or reduced-capability contexts.

No strong memory corruption, UAF, OOB write, arbitrary write, or demonstrated LPE primitive is supported by the patch.

## 3. Reachability analysis

The bug is triggered through local Generic Netlink NetLabel configuration, not by remote packets. In typical deployments, this path requires CAP_NET_ADMIN or equivalent administrative control over NetLabel policy. Namespace or container delegation may lower the practical privilege boundary if CAP_NET_ADMIN is granted to a reduced-privilege context. NetLabel is not a broad default user-facing path, but it is security-sensitive when enabled and used.

## 4. Severity interpretation

This behaves more like a borderline Moderate issue than an Important-class vulnerability. The concrete primitive is a limited OOB read / invalid mask interpretation in a security policy configuration path. The realistic impact is policy integrity risk and possible DoS, while privilege escalation is not demonstrated. The paranoid score is higher because the affected subsystem enforces labeling policy and delegated CAP_NET_ADMIN environments may make the bug more actionable.

## 5. One-sentence report phrase

A crafted local NetLabel Generic Netlink request can provide a valid IPv4 or IPv6 address with a short mask attribute, causing the kernel to read the mask as a full address-sized structure and potentially affecting NetLabel policy handling or stability.

## 6. Manual review recommendation

MANUAL CHECK RECOMMENDED

Manual review is recommended because this is an OOB read in a security-labeling subsystem, but it should not be treated as Strong Important by default because the patch does not show UAF, OOB write, arbitrary write, information disclosure to userspace, or a concrete privilege-escalation path.

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

Patch: netlabel: validate unlabeled address and mask attribute lengths [ Upstream
Commit: 975a84fd741440853380d37465b6e226cf47254c
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=975a84fd741440853380d37465b6e226cf47254c

Changed files:
  net/netlabel/netlabel_unlabeled.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=975a84fd741440853380d37465b6e226cf47254c

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

The original Linux kernel CVE announcement for CVE-2026-53238 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53238

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:L/A:L
  The Best / paranoid CVSS vector: AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:H
  The Best / paranoid CVSS score: 6.6

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: 2
  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).