[CVE-2026-72183][IMPORTANT] landlock: Fix LANDLOCK_SCOPE_SIGNAL bypass on the SIGIO path [ Upstream

[CVE-2026-72183][IMPORTANT] landlock: Fix LANDLOCK_SCOPE_SIGNAL bypass on the SIGIO path [ Upstream

[AL-KERNEL]

CVE: CVE-2026-72183
Priority: IMPORTANT
AL-KERNEL base severity: IMPORTANT
KPANIC flag: YES
Patch: landlock: Fix LANDLOCK_SCOPE_SIGNAL bypass on the SIGIO path [ Upstream
Commit: 7a92e9fd1d496a610b40e0c4253fd54e7496f5ab
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=7a92e9fd1d496a610b40e0c4253fd54e7496f5ab
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72183
Analysis date: Sat, 15 Aug 2026 14:59:47 -0400
ActionableScore: 7
ActionableScore lower bound: unknown
Actionable bucket: Strong Important candidate / Actionable Moderate at minimum
Manual review required: YES

Summary:
No one-sentence report phrase was found.

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

The original Linux kernel CVE announcement for CVE-2026-72183 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72183

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: IMPORTANT
Manual review required: YES

A detailed explanation of the methodology and priority rules is included
at the end of this message.

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

CVE-2026-72183	IMPORTANT	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:L/UI:N/S:C/C:N/I:H/A:H';CWE-863;CWE-284;CWE-693;Other CVSS 'AV:L/AC:L/PR:L/UI:N/S:C/C:N/I:L/A:H';BEST CVSS score: '8.4';DESCR 'LANDLOCK_SCOPE_SIGNAL can be bypassed on the asynchronous SIGIO delivery path because the Landlock domain recorded at F_SETOWN time may be missing for process group or session owners. A sandboxed local process that owns a file or socket can arrange asynchronous I/O signal delivery to a process group and may signal non sandboxed processes in the same group, such as a supervisor or security monitor. For the CVSS the PR:L value is used because the attacker needs local code execution inside a Landlock sandbox but does not need administrative privileges. The issue is not directly network reachable and is not memory corruption. Impact is a Landlock signal scope bypass with possible unauthorized SIGKILL or other signal delivery outside the sandbox, causing integrity impact and denial of service.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Strong Important candidate / Actionable Moderate at minimum (with actual score 7)	YES	LINUS  KPANIC INCREASED_TO_MODERATE_FROM_LOW_BASED_ON_GUESSCVSS KPANIC INCREASED_TO_HIGH_BASED_ON_ACTIONABLESCOREHIGHEREQTHAN6	YES	NO	checked

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

ActionableScore=7

1. **ActionableScore**
* Conservative score: 7
* Paranoid score: 7
* Final recommended bucket: **Strong Important candidate / Actionable Moderate at minimum**::

2. **Signal breakdown**
* Local unprivileged trigger: +1. A sandboxed local process can use ordinary file or socket ownership operations with fcntl and O_ASYNC.
* Security-boundary bypass with practical sensitive-object access: +2. The bug bypasses LANDLOCK_SCOPE_SIGNAL, an intended LSM sandbox boundary.
* Cross-boundary isolation/policy bypass: +1. A process inside a Landlock domain can affect processes outside that domain.
* Practical exploit chain demonstrated or strongly implied: +1. The commit gives a concrete sequence using F_SETOWN, F_SETSIG, SIGKILL and O_ASYNC.
* Integrity impact plausible: +1. Unauthorized signal delivery violates the intended process-control policy.
* Availability impact realistic: +1. SIGKILL or disruptive signals can terminate supervisors, monitors, or other protected processes.
* No memory corruption signals. The patch fixes policy enforcement and lifetime tracking of stored domain/thread-group state, not UAF/OOB/write corruption.

3. **Reachability analysis**
The trigger is local and does not require administrative privileges, but it requires execution inside a Landlock sandbox and a suitable file or socket that can generate SIGIO. Network reachability does not apply directly. Containers or sandboxed service models increase relevance because the bug crosses a reduced-privilege security boundary rather than requiring full host root. The path is only security-relevant on systems using Landlock with LANDLOCK_SCOPE_SIGNAL, but the exploitation conditions are practical in such deployments.

4. **Severity interpretation**
This behaves more like an Important-class access-control bypass than an ordinary Moderate DoS. There is no evidence of kernel memory corruption or arbitrary code execution. The important aspect is that a sandboxed process can signal or kill non-sandboxed processes that Landlock was specifically meant to protect, including possible supervisors or security monitors. Realistic impact is policy bypass plus availability disruption, with high integrity concern in the sandbox model.

5. **One-sentence report phrase**
A Landlock SIGIO policy bypass allows a sandboxed local process to use asynchronous I/O ownership on a file or socket to deliver signals such as SIGKILL to processes outside its Landlock domain, causing unauthorized cross-domain process control and denial of service.

6. **Manual review recommendation**
MANUAL CHECK REQUIRED. This is a security-boundary bypass in an LSM sandbox feature with a concrete trigger path and possible impact on supervisors or security monitors, so it should not be auto-closed.

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

Patch: landlock: Fix LANDLOCK_SCOPE_SIGNAL bypass on the SIGIO path [ Upstream
Commit: 7a92e9fd1d496a610b40e0c4253fd54e7496f5ab
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=7a92e9fd1d496a610b40e0c4253fd54e7496f5ab

Changed files:
  security/landlock/fs.c
  security/landlock/fs.h
  security/landlock/task.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=7a92e9fd1d496a610b40e0c4253fd54e7496f5ab

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

The original Linux kernel CVE announcement for CVE-2026-72183 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72183

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:C/C:N/I:L/A:H
  The Best / paranoid CVSS vector: AV:L/AC:L/PR:L/UI:N/S:C/C:N/I:H/A:H
  The Best / paranoid CVSS score: 8.4

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: unknown
  Paranoid ActionableScore: 7

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: IMPORTANT
KPANIC detected for this report: YES
Published priority for this report (same as in Subject): IMPORTANT

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).