[CVE-2026-64412][MODERATE REGULAR] netfilter: ebtables: module names must be null-terminated

[CVE-2026-64412][MODERATE REGULAR] netfilter: ebtables: module names must be null-terminated

[AL-KERNEL]

CVE: CVE-2026-64412
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: netfilter: ebtables: module names must be null-terminated
Commit: 43dd2332b8a27b3ac5108791680cade654ab0f96
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=43dd2332b8a27b3ac5108791680cade654ab0f96
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64412
Analysis date: Sat, 25 Jul 2026 06:50:35 -0400
ActionableScore: 4
ActionableScore lower bound: 2
Actionable bucket: Borderline. Manual check required before auto-close
Manual review required: YES

Summary:
ebtables failed to validate that a user supplied extension name was NUL terminated before lookup and module autoload, allowing a CAP_NET_ADMIN capable local actor to trigger a kernel string overread with possible DoS or limited disclosure impact.

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

The original Linux kernel CVE announcement for CVE-2026-64412 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64412

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-2026-64412	MODERATE	CHECK WITH IMPACT FROM ORIG NN IMPORTANT	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:N/A:H';CWE-170;CWE-126;*CWE-20;Other CVSS 'AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:L';BEST CVSS score: '5.3';DESCR 'ebtables accepted an extension name from a rule blob without verifying that the name is NUL terminated before passing it to xt_find_match and request_module. A local process able to update ebtables rules can provide a maximum length name without a terminator, causing kernel string handling to read beyond the fixed name field. For the CVSS the PR:L is used because reliable triggering requires local rule update capability such as CAP_NET_ADMIN, which may be delegated to a service account, container root, or network namespace user rather than full host root. The issue is not directly network reachable and is triggered through firewall control plane configuration, not by bridge packet traffic. Impact is mainly denial of service or warning through an out of bounds read, with at most limited confidentiality concern if adjacent kernel bytes influence the module request string.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline. Manual check required before auto-close (with actual score 3)	YES	SIMPLEFIX NETFILTER IMPROVEONLY LINUS  LOWERED_FROM_HIGH_BASED_ON_GUESSCVSS  DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5	NO	NO	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=4
ActionableScoreLower=2

## 1. ActionableScore

* Conservative score: 2
* Paranoid score: 4
* Final recommended bucket: **Borderline. Manual check required before auto-close**::

## 2. Signal breakdown

Conservative signals:

* +1 Weak memory safety candidate: the missing NUL termination check can cause kernel C string handling to read beyond the fixed ebtables extension name field.
* +1 Availability impact realistic: passing a non-NUL-terminated name into lookup or module autoload paths can plausibly trigger an OOB read, warning, or crash, although no strong crash primitive is demonstrated.
* +1 Confidentiality impact plausible: adjacent bytes could theoretically influence the module request string or logs, but there is no clear reliable information disclosure channel.
* +1 Broad subsystem exposure: netfilter is a common subsystem, although this is ebtables control plane rather than packet-processing fast path.
* -2 Requires CAP_NET_ADMIN in typical deployments: updating ebtables rules is normally privileged.

Paranoid adjustment:

* +1 Local delegated trigger concern: CAP_NET_ADMIN may be delegated to container root, service accounts, or network namespaces in some deployments.
* +1 Reduced privilege penalty interpretation: this is not necessarily full host-root in practical risk terms, so the privilege penalty can be softened in paranoid triage.

No strong signals:

* No OOB write, UAF, double-free, type confusion, controlled overwrite, callback hijack, or demonstrated LPE primitive is shown.
* Not network-triggerable by bridge traffic alone.

## 3. Reachability analysis

The bug is triggered through ebtables rule installation or update, not by receiving network packets. A typical attacker needs CAP_NET_ADMIN or equivalent control over bridge netfilter rules. In default hardened deployments this is privileged, but in containerized or namespace-enabled environments CAP_NET_ADMIN may be delegated to less trusted contexts, which supports the paranoid score. The affected path is not a remote network parser, and exploitation depends on being able to submit a crafted ebtables match name without NUL termination.

Call-site confidence: medium. The patch directly shows the unchecked name reaching xt_find_match(), and the commit states that request_module() may receive the non-NUL-terminated string, but the full downstream request_module call chain is not included in the snippet.

## 4. Severity interpretation

This behaves like a borderline Moderate issue rather than an Important-class vulnerability. The practical concern is a kernel OOB read through string handling in a privileged netfilter control-plane path. Theoretical impact includes limited disclosure or crash, but the patch does not support strong memory corruption, arbitrary write, privilege escalation, or direct network reachability. Manual review is still warranted because kernel string overreads reaching request_module() can have subtle behavior.

## 5. One-sentence report phrase

ebtables failed to validate that a user supplied extension name was NUL terminated before lookup and module autoload, allowing a CAP_NET_ADMIN capable local actor to trigger a kernel string overread with possible DoS or limited disclosure impact.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED

Reason: the score is not Important-level, but this is a kernel OOB read candidate in netfilter control-plane code and the string reaches module autoload logic, so it should not be blindly auto-closed without checking product namespace and CAP_NET_ADMIN exposure.

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

Patch: netfilter: ebtables: module names must be null-terminated
Commit: 43dd2332b8a27b3ac5108791680cade654ab0f96
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=43dd2332b8a27b3ac5108791680cade654ab0f96

Commit description:

We need to explicitly check the length, else we may pass non-null
terminated string to request_module().

Cc: stable@vger.kernel.org
Fixes: bcf4934 ("netfilter: ebtables: Fix extension lookup with identical name")
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  net/bridge/netfilter/ebtables.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=43dd2332b8a27b3ac5108791680cade654ab0f96

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

The original Linux kernel CVE announcement for CVE-2026-64412 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64412

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