[CVE-2026-72142][LOW] i2c: imx: fix locked bus on SMBus block-read of 0 (atomic) [ Upstream

[CVE-2026-72142][LOW] i2c: imx: fix locked bus on SMBus block-read of 0 (atomic) [ Upstream

[AL-KERNEL]

CVE: CVE-2026-72142
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: i2c: imx: fix locked bus on SMBus block-read of 0 (atomic) [ Upstream
Commit: 016ef0f6ca4bc9bf0330ac41bd2ea349759643e3
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=016ef0f6ca4bc9bf0330ac41bd2ea349759643e3
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72142
Analysis date: Sun, 16 Aug 2026 08:12:05 -0400
ActionableScore: 2
ActionableScore lower bound: 1
Actionable bucket: Ordinary Moderate / Low-like
Manual review required: NO

Summary:
The i2c-imx atomic SMBus block-read path can leave the bus stuck when a target returns a zero or oversized block count, causing a persistent denial of service for the affected I2C controller until recovery or power cycle.

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

The original Linux kernel CVE announcement for CVE-2026-72142 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72142

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-2026-72142	LOW	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:N/I:N/A:H';CWE-754;CWE-755;CWE-667;Other CVSS 'AV:P/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '5.5';DESCR 'The i2c imx atomic SMBus block read path can leave the bus locked when the target returns a block count of 0 or a count above I2C_SMBUS_BLOCK_MAX. After reading I2DR the next receive cycle is already armed, but the old error path returned before issuing NACK and STOP, so the target may keep SDA asserted and the controller bus can remain stuck until a power cycle. For the CVSS the PR:L is used in the paranoid local scenario because a local user or service with access to I2C device interfaces may be able to issue SMBus block read operations. The base hardware scenario can also be triggered by a faulty or malicious SMBus target without OS privileges. The issue is not network reachable and the impact is denial of service for the affected I2C bus or controller. There is no evidence of memory corruption, information disclosure, or privilege escalation.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like (with actual score 2)	YES	USB LINUS  INCREASED_FROM_LOW_BASED_ON_HIGHCVSSSCORE DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5 DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3	NO	NO	checked

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

ActionableScore=2
ActionableScoreLower=1

## 1. ActionableScore

* Conservative score: **1**
* Paranoid score: **2**
* Final recommended bucket: **Ordinary Moderate / Low-like**::

## 2. Signal breakdown

Conservative signals:

* **Firmware-mediated external influence: +1**. A faulty or malicious SMBus/I2C target can return block count 0 or an oversized count and influence the controller state.
* **Reliable strong DoS: +1**. The bus can remain stuck with SDA held until power cycle for this I2C controller.
* **Availability impact realistic: +1**. The DoS is persistent for the affected I2C bus/controller, not just a transient failed transaction.
* **Physical-only or rare hardware-only condition: -2**. Realistic triggering depends on the affected i2c-imx controller and a target device returning the problematic SMBus count.

Paranoid additional interpretation:

* **Local unprivileged trigger: +1**. If a local user or service has access to `/dev/i2c-*` or another exposed I2C interface, it may be able to initiate the SMBus block read path.
* No memory corruption, UAF, OOB write, privilege escalation, confidentiality impact, or integrity impact is supported by the patch.

## 3. Reachability analysis

The bug is reachable through the atomic SMBus block-read path in the `i2c-imx` driver. A malicious or faulty I2C/SMBus target can trigger it by returning a block count of 0 or a count greater than `I2C_SMBUS_BLOCK_MAX`. A local process may also trigger the transaction if the system exposes I2C access through `i2c-dev` or a similar interface, but such access is commonly restricted by permissions or device policy.

This is not network reachable. Containers and namespaces generally do not lower the requirement unless the I2C device node is explicitly passed through. The affected path is hardware and platform dependent, so exposure is limited to systems using the affected i.MX I2C controller and SMBus block reads.

Call-site confidence: **high**, because the relevant read path and error handling behavior are visible in the patch.

## 4. Severity interpretation

This behaves like an **ordinary Moderate / Low-like hardware DoS** issue. The practical impact is a persistent lockup of the affected I2C bus until power cycle, which can be operationally significant on embedded systems. However, there is no evidence of kernel memory corruption, privilege escalation, information disclosure, filesystem corruption, or cross-boundary policy bypass.

The paranoid score accounts for local users with delegated I2C device access, but the vulnerability class remains DoS-only.

## 5. One-sentence report phrase

The i2c-imx atomic SMBus block-read path can leave the bus stuck when a target returns a zero or oversized block count, causing a persistent denial of service for the affected I2C controller until recovery or power cycle.

## 6. Manual review recommendation

**NO MANUAL CHECK NEEDED**

This is a platform-specific I2C/SMBus availability bug with no demonstrated memory corruption or privilege-escalation primitive. Manual review may only be useful for products where the affected I2C bus controls safety-critical or availability-critical hardware.

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

Patch: i2c: imx: fix locked bus on SMBus block-read of 0 (atomic) [ Upstream
Commit: 016ef0f6ca4bc9bf0330ac41bd2ea349759643e3
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=016ef0f6ca4bc9bf0330ac41bd2ea349759643e3

Changed files:
  drivers/i2c/busses/i2c-imx.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=016ef0f6ca4bc9bf0330ac41bd2ea349759643e3

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

The original Linux kernel CVE announcement for CVE-2026-72142 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72142

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:P/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS vector: AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS score: 5.5

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).