[CVE-2026-72141][LOW] i2c: imx: fix locked bus on SMBus block-read of 0 (IRQ)

[CVE-2026-72141][LOW] i2c: imx: fix locked bus on SMBus block-read of 0 (IRQ)

[AL-KERNEL]

CVE: CVE-2026-72141
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: i2c: imx: fix locked bus on SMBus block-read of 0 (IRQ)
Commit: 5d3240f42a667e29262aff76fdebfcdac4980626
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=5d3240f42a667e29262aff76fdebfcdac4980626
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72141
Analysis date: Sun, 16 Aug 2026 05:08:32 -0400
ActionableScore: 2
ActionableScore lower bound: 1
Actionable bucket: Ordinary Moderate / Low-like
Manual review required: NO

Summary:
No one-sentence report phrase was found.

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

The original Linux kernel CVE announcement for CVE-2026-72141 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72141

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-2026-72141	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-400;Other CVSS 'AV:P/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '5.5';DESCR 'An i2c-imx SMBus block read can leave the I2C bus stuck because the IRQ state machine rejects a block read count 0 or an invalid oversized count after the next receive cycle has already started. A malicious or faulty I2C/SMBus target can keep SDA held when the driver returns without issuing the required NACK and STOP sequence, making the bus unavailable until the affected controller is power cycled. For the CVSS the PR:L is used in the paranoid local scenario because reliable software triggering would require a local user or service that can initiate SMBus block reads through an exposed I2C interface. The issue is not network reachable and does not indicate memory corruption, information disclosure, or privilege escalation. Impact is denial of service limited to the affected I2C controller and dependent devices, but it may be operationally significant on embedded systems where that bus controls critical peripherals.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like (with actual score 2)  SKIP CVE-2026-72141 UNKNOWN SKIP The Fixes patch not applied yet, so unlikely that actual: 5f5c2d4579ca6836f5604cca979debd68ecfe23f YES  NO NO unknown 	MAYBE	DANGER USB ERRORPATH DMAorINTERRUPT LINUS MEMORY  DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS_AND_CIANNH DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3	-	-	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
* Firmware-mediated external influence: +1. A malicious or faulty SMBus/I2C target can return count 0 or an oversized count and influence the controller state.
* Reliable device-level DoS: +1. The bus can remain stuck with SDA held until the affected controller is power-cycled.
* Availability impact realistic: +1 in the paranoid score only. The DoS is persistent for the controller and dependent devices, but not necessarily host-wide.
* Physical-only or rare hardware-only condition: -2. The primary trigger requires a specific i2c-imx controller and a hostile or faulty device on the I2C/SMBus bus.
* Rare and hardware-specific exposure: -1 in the conservative interpretation. This is not a broad default kernel attack surface and is limited to affected hardware and SMBus block-read usage.
* No memory corruption signal. The patch fixes protocol/state handling with NACK/STOP and does not show UAF, OOB write, double-free, type confusion, or page ownership corruption.
* No privilege escalation signal. The described consequence is bus lockup, not LPE or security-boundary bypass.

3. Reachability analysis
The most realistic attacker is a malicious, compromised, or faulty I2C/SMBus target device that can return a block-read count of 0 or an invalid oversized count. A local software trigger is only plausible if a local user or service can initiate SMBus block reads through an exposed I2C interface such as i2c-dev, which is not normally available to arbitrary unprivileged users in hardened deployments. Namespaces and containers usually do not lower the requirement unless the device node is deliberately passed through. The path is hardware and driver specific, not network reachable, and exploitation conditions depend on affected i2c-imx hardware plus SMBus block-read traffic.

4. Severity interpretation
This behaves like a device-level DoS issue rather than an Important-class kernel vulnerability. The impact can be operationally significant on embedded systems if critical peripherals share the affected bus, but the patch does not support memory corruption, confidentiality impact, integrity impact, or privilege escalation. Theoretical worst case is a persistent local or hardware-mediated availability loss for the affected controller, not host compromise.

5. One-sentence report phrase
An i2c-imx SMBus block read with count 0 or an invalid oversized count can leave the controller without a proper NACK and STOP sequence, allowing a malicious or faulty I2C target to hold SDA and lock the bus until controller power cycle.

6. Manual review recommendation
NO MANUAL CHECK NEEDED.
The issue is DoS-only, hardware-specific, not network reachable, and has no supported memory corruption or privilege escalation primitive. Call-site confidence: high, because the relevant ISR state-machine path and the NACK/STOP fix are visible in the supplied patch.

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

Patch: i2c: imx: fix locked bus on SMBus block-read of 0 (IRQ)
Commit: 5d3240f42a667e29262aff76fdebfcdac4980626
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=5d3240f42a667e29262aff76fdebfcdac4980626

Commit description:

SMBus 3.1 6.5.7 allows a Block Read byte count of 0, but the
interrupt-driven block-read state machine rejects it as -EPROTO. Worse,
it returns without a NACK+STOP: the next receive cycle has already
started, so the target keeps holding SDA and the bus stays stuck until a
power cycle of this i2c controller.

Accept count=0: NACK the in-flight dummy byte (TXAK) and set msg->len to
2 so i2c_imx_isr_read_continue() emits STOP via its normal last-byte
path. The dummy byte is discarded; block-read callers only consume
buf[0..count-1].

Reading I2DR has likewise already armed the next byte on the
count > I2C_SMBUS_BLOCK_MAX error path, so NACK it (TXAK) before aborting
with -EPROTO; otherwise the failing transfer's STOP cannot complete and
the bus stays held.

The atomic path regressed earlier (v3.16) and is fixed separately; this
patch covers only the v6.13 state-machine rework.

Fixes: 5f5c2d4 ("i2c: imx: prevent rescheduling in non dma mode")
Signed-off-by: Vincent Jardin <vjardin@free.fr>
Cc: <stable@vger.kernel.org> # v6.13+
Acked-by: Oleksij Rempel <o.rempel@pengutronix.de>
Acked-by: Carlos Song <carlos.song@nxp.com>
Reviewed-by: Stefan Eichenberger <eichest@gmail.com>
Signed-off-by: Andi Shyti <andi.shyti@kernel.org>
Link: https://lore.kernel.org/r/20260713-for-upstream-i2c-lx2160-fix-v1-v3-2-073ac9e103a5@free.fr
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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=5d3240f42a667e29262aff76fdebfcdac4980626

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

The original Linux kernel CVE announcement for CVE-2026-72141 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72141

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).