[CVE-2026-72424][LOW] rtc: msc313: fix NULL deref in shared IRQ handler at probe [ Upstream

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

CVE: CVE-2026-72424
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: rtc: msc313: fix NULL deref in shared IRQ handler at probe [ Upstream
Commit: ece7b9ffde23e2ccd7567761ac27463ded43932c
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=ece7b9ffde23e2ccd7567761ac27463ded43932c
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72424
Analysis date: Sun, 16 Aug 2026 08:25:54 -0400
ActionableScore: 1
ActionableScore lower bound: 0
Actionable bucket: Ordinary Moderate / Low-like
Manual review required: NO

Summary:
A probe-time race in the MSC313 RTC shared IRQ handler can allow an interrupt to dereference NULL driver data and crash the kernel, but exploitation requires narrow timing and device-management conditions and does not indicate privilege escalation.

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

The original Linux kernel CVE announcement for CVE-2026-72424 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72424

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.

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

CVE-2026-72424	LOW	CHECK WITH IMPACT FROM ORIG NN LOW	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H';**CWE-476;CWE-362;CWE-665;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '4.7';DESCR 'A NULL pointer dereference can occur in the msc313 RTC shared IRQ handler during driver probe. The handler was registered before driver data was available, so an interrupt from another device on the same shared IRQ line could make dev_get_drvdata() return NULL and then dereference rtc_base in interrupt context. This is a narrow probe time race and initialization ordering issue. For the CVSS the PR:L reflects the paranoid case where a local user or constrained service can indirectly cause driver bind or interrupt activity through delegated device management. The issue is not network reachable. Impact is local denial of service via kernel crash only, with no supported path to information disclosure or privilege escalation.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like (with actual score 1)  SKIP CVE-2026-72424 UNKNOWN SKIP No affected files built, so skip this CVE NO  - - unknown 	MAYBE	SIMPLEFIX HARDWARE LINUS 	-	-	checked

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

ActionableScore=1
ActionableScoreLower=0

## 1. ActionableScore

* Conservative score: 0
* Paranoid score: 1
* Final recommended bucket: **Ordinary Moderate / Low-like**

## 2. Signal breakdown

Conservative scoring:

* Reliable kernel crash / strong DoS: +1. NULL dereference of `priv->rtc_base` in interrupt context can crash the kernel.
* Hard or unreliable race / special timing required: -1. The interrupt must arrive in a narrow probe window after `devm_request_irq()` but before `platform_set_drvdata()`.
* Requires admin/root/CAP_* in typical deployments: -2. Reliable triggering usually requires driver probe, reprobe, bind/unbind, boot-time device setup, or device-management control.
* Rare AND difficult-to-reach subsystem/configuration: -1. This is specific to the MSC313 RTC driver, shared IRQ configuration, and probe timing.
* No memory corruption / LPE signal: +0. This is a NULL pointer dereference, not UAF, OOB write, type confusion, refcount abuse, or callback corruption.

Paranoid scoring:

* Reliable kernel crash / strong DoS: +1.
* Local indirect trigger possibility: +1. In a permissive or delegated device-management environment, a local user or constrained service might indirectly influence reprobe or interrupt activity.
* Hard or unreliable race / special timing required: -1.
* Result: 1.

Call-site confidence: high. The changed IRQ registration call and the interrupt handler are both present in the patch.

## 3. Reachability analysis

The bug is local and device/probe dependent. It is not network reachable. In normal deployments, the attacker would need control over driver probing or a way to cause activity on another device sharing the IRQ during the small initialization window. Namespaces do not normally make this reachable by an unprivileged user. Container impact is only plausible if device-management capabilities or relevant host device access are delegated into the container.

The affected path is not a broad default kernel interface. It depends on MSC313 RTC hardware or platform support, shared IRQ behavior, and timing during driver probe.

## 4. Severity interpretation

This behaves like a low-end Moderate or Low-like kernel DoS issue. The theoretical impact is a kernel crash from a NULL pointer dereference in interrupt context. There is no supported evidence of memory corruption beyond NULL dereference, no stale object reuse, no UAF, no write primitive, no information disclosure, and no plausible privilege escalation path.

The paranoid interpretation only raises the score slightly for unusual delegated device-management cases, not because the bug class suggests LPE.

## 5. One-sentence report phrase

A probe-time race in the MSC313 RTC shared IRQ handler can allow an interrupt to dereference NULL driver data and crash the kernel, but exploitation requires narrow timing and device-management conditions and does not indicate privilege escalation.

## 6. Manual review recommendation

NO MANUAL CHECK NEEDED

Reason: DoS-only NULL dereference, narrow probe-time race, hardware-specific path, no network reachability, and no concrete memory corruption or privilege-escalation primitive.

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

Patch: rtc: msc313: fix NULL deref in shared IRQ handler at probe [ Upstream
Commit: ece7b9ffde23e2ccd7567761ac27463ded43932c
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=ece7b9ffde23e2ccd7567761ac27463ded43932c

Changed files:
  drivers/rtc/rtc-msc313.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=ece7b9ffde23e2ccd7567761ac27463ded43932c

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

The original Linux kernel CVE announcement for CVE-2026-72424 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72424

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:H/PR:H/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS score: 4.7

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: 0
  Paranoid ActionableScore: 1

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).