[CVE-2026-72018][MODERATE 7.0] dibs: loopback: validate offset and size in move_data() commit 78237e3c0720fcc6eb9b87e90fd70f63eeca886f upstream.

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

CVE: CVE-2026-72018
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: dibs: loopback: validate offset and size in move_data() commit 78237e3c0720fcc6eb9b87e90fd70f63eeca886f upstream.
Commit: ee188a6b264b71315a67f1b9470faad308b730d2
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=ee188a6b264b71315a67f1b9470faad308b730d2
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72018
Analysis date: Sat, 15 Aug 2026 10:12:25 -0400
ActionableScore: 8
ActionableScore lower bound: 5
Actionable bucket: Strong Important candidate / Actionable Moderate at minimum
Manual review required: YES

Summary:
A peer supplied offset and size in the DIBS loopback move_data path can trigger a kernel OOB write past a registered DMB buffer, making this a local memory corruption issue with realistic DoS impact and plausible privilege escalation concern.

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ABOUT THIS REPORT
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The original Linux kernel CVE announcement for CVE-2026-72018 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72018

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 7.0
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-2026-72018	MODERATE	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:U/C:H/I:H/A:H';*CWE-787;*CWE-20;CWE-119;Other CVSS 'AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:H';BEST CVSS score: '7.8';DESCR 'A peer supplied offset and size in the DIBS loopback move_data path can reach memcpy into a registered DMB without a bounds check. This allows an OOB write past the allocated kernel buffer because the software loopback path lacks the hardware memory region enforcement that real ISM hardware provides. For the CVSS the PR:L is selected because a local user or local peer process is normally needed to create the SMC/DIBS loopback communication path and supply the malicious offset and size. The issue is not treated as directly Internet reachable from the patch context because it affects a loopback software transport path rather than normal remote packet processing. Impact is at least local denial of service via kernel memory corruption and in the paranoid case may include confidentiality and integrity impact or privilege escalation.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Strong Important candidate / Actionable Moderate at minimum (with actual score 7)  SKIP CVE-2026-72018 UNKNOWN SKIP No affected files built, so skip this CVE NO  - - unknown 	MAYBE	WRITE OOB LOCK SIMPLEFIX HARDWARE KPANIC  KPANIC INCREASED_TO_HIGH_BASED_ON_GUESSCVSS DECREASED_TO_MODERATE7_BASED_ON_FALSEPOSCHECKOFKP	-	-	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=8
ActionableScoreLower=5

## 1. ActionableScore

* Conservative score: 5
* Paranoid score: 8
* Final recommended bucket: **Strong Important candidate / Actionable Moderate at minimum**::

## 2. Signal breakdown

Conservative signals:

* Local unprivileged trigger: +1. The affected path is a loopback SMC/DIBS peer data path and appears reachable by a local peer process rather than requiring full host root.
* Memory corruption, strong corruption primitive: +2. The commit explicitly says a peer supplied out of bounds offset or oversized write causes an OOB write past an allocated kernel buffer.
* Weak LPE concern: +1. The primitive is a kernel OOB write with peer influenced offset and size, but the patch does not demonstrate a reliable target selection or exploit chain.
* Reliable kernel crash / strong DoS: +1. Kernel heap OOB write is a realistic crash or panic condition.
* Rare and configuration dependent subsystem: -1. DIBS loopback / loopback ISM is less broadly exposed than common TCP/IP packet processing or core socket paths.
* Privileged kernel/device-management memory corruption path: +1. The corruption occurs inside a trusted kernel transport/device abstraction managing registered DMB buffers.

Paranoid additional interpretation:

* Strong LPE plausibility: +2 instead of weak +1. A peer controlled kernel OOB write may be groomable into corruption of adjacent kernel objects, even though this is not proven by the patch.
* Confidentiality impact plausible: +1. If the OOB write can corrupt kernel objects or metadata, secondary disclosure paths are possible.
* Integrity impact plausible: +1. The primitive is a direct write beyond a kernel allocation and can plausibly corrupt kernel state.

## 3. Reachability analysis

The bug is not directly Internet reachable from the patch context. It affects the software loopback DIBS path used by SMC related local peer communication, not normal remote packet parsing. A local user or local process able to create the relevant SMC/DIBS loopback communication can potentially supply the malicious offset and size. No CAP_SYS_ADMIN or CAP_NET_ADMIN requirement is shown in the provided patch, so PR:L is the safer practical assumption. Namespaces may matter if SMC sockets and the loopback device path are exposed inside containers, but the provided context does not prove container escape reachability. Call-site confidence: medium, because the changed function and memcpy sink are visible, but broader caller and deployment gating are not included.

## 4. Severity interpretation

This is above ordinary Moderate because the patch fixes an explicit peer influenced kernel OOB write, not just validation cleanup or a crash-only NULL dereference. The conservative interpretation is Actionable Moderate because exploitation conditions depend on local access to a relatively specialized loopback SMC/DIBS path. The paranoid interpretation is a Strong Important candidate because controlled offset and size reaching memcpy past a kernel buffer is a classic memory corruption primitive with plausible privilege escalation potential. Realistic exploitation is not demonstrated, so Critical level is not justified.

## 5. One-sentence report phrase

A peer supplied offset and size in the DIBS loopback move_data path can trigger a kernel OOB write past a registered DMB buffer, making this a local memory corruption issue with realistic DoS impact and plausible privilege escalation concern.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED

Reason: this is an explicit peer influenced kernel OOB write into an allocated kernel buffer. Even though the affected loopback transport is not broadly remote reachable, the memory corruption primitive is strong enough that it should not be auto-closed.

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

Patch: dibs: loopback: validate offset and size in move_data() commit 78237e3c0720fcc6eb9b87e90fd70f63eeca886f upstream.
Commit: ee188a6b264b71315a67f1b9470faad308b730d2
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=ee188a6b264b71315a67f1b9470faad308b730d2

Commit description:

The loopback move_data() performs a memcpy into the registered DMB
without checking whether offset + size exceeds the DMB length.  Unlike
real ISM hardware, which enforces memory region bounds natively, the
software loopback has no such protection.

A peer-supplied out-of-bounds offset or oversized write would result in
an OOB write past the allocated kernel buffer.  Add an explicit bounds
check before the memcpy to reject such requests with -EINVAL.

Fixes: f7a22071dbf3 ("net/smc: implement DMB-related operations of loopback-ism")
Cc: stable@vger.kernel.org
Reported-by: Federico Kirschbaum <federico.kirschbaum@xbow.com>
Signed-off-by: Dust Li <dust.li@linux.alibaba.com>
Reported-by: Baul Lee <baul.lee@xbow.com>
Link: https://patch.msgid.link/20260707074318.1448662-1-dust.li@linux.alibaba.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
[backport for smc_loopback instead of dibs_loopback]
Signed-off-by: Dust Li <dust.li@linux.alibaba.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat -rw-r--r-- net/smc/smc_loopback.c 5

Changed files:
  net/smc/smc_loopback.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=ee188a6b264b71315a67f1b9470faad308b730d2

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

The original Linux kernel CVE announcement for CVE-2026-72018 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72018

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:L/A:H
  The Best / paranoid CVSS vector: AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
  The Best / paranoid CVSS score: 7.8

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: 5
  Paranoid ActionableScore: 8

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: YES
Published priority for this report (same as in Subject): MODERATE 7.0

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).