[CVE-2026-74329][MODERATE 7.0] watchdog: unregister PM notifier on watchdog unregister [ Upstream

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

CVE: CVE-2026-74329
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: watchdog: unregister PM notifier on watchdog unregister [ Upstream
Commit: cd2d1b1f99308f7680d75a377daaff363f1cc736
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=cd2d1b1f99308f7680d75a377daaff363f1cc736
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74329
Analysis date: Sat, 15 Aug 2026 04:30:23 -0400
ActionableScore: 5
ActionableScore lower bound: 2
Actionable bucket: Actionable Moderate at minimum
Manual review required: YES

Summary:
A stale PM notifier can remain registered after watchdog device unregister, allowing a later suspend or resume event to call watchdog_pm_notifier on a torn down watchdog_device and causing at least a local kernel crash, with a defensible worst case UAF concern.

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

The original Linux kernel CVE announcement for CVE-2026-74329 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74329

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.

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

CVE-2026-74329	MODERATE	CHECK WITH IMPACT FROM ORIG NN MODERATE	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H';*CWE-416;CWE-459;*CWE-672;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '7';DESCR 'A stale PM notifier can remain registered after watchdog device unregister when WDOG_NO_PING_ON_SUSPEND is set. A later suspend or resume notification may call watchdog_pm_notifier through an unregistered watchdog_device or after wd_data has been cleared, causing a kernel crash and potentially a use-after-free if the embedded notifier memory was freed and reused. For the CVSS the PR:L is used in the paranoid case because some deployments may delegate device unbind, hotplug, or suspend control to a reduced local account rather than full administrator access. The issue is not network reachable and requires local control over the watchdog device lifecycle or power management path. Impact is at least local denial of service via kernel crash and in worst case may allow confidentiality and integrity impact due to a stale notifier based use-after-free. For the paranoid score, choose the highest still-defensible interpretation supported by the bug class and patch context, with preference for manual-review sensitivity over autoclosed false negatives.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 4)	YES	INIT SIMPLEFIX HARDWARE  INCREASED_TO_MODERATE7_BASED_ON_GUESSCVSS DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5	YES	NO	guess

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

ActionableScore=5
ActionableScoreLower=2

## 1. ActionableScore

* Conservative score: 2
* Paranoid score: 5
* Final recommended bucket: **Actionable Moderate at minimum**::

## 2. Signal breakdown

Conservative signals:

* Real lifetime corruption: +1. The PM notifier remains registered after watchdog unregister, leaving a stale embedded notifier block tied to watchdog_device lifetime.
* Reliable kernel crash / strong DoS: +1. A later suspend/resume notification can call watchdog_pm_notifier after teardown or after wdd->wd_data is cleared.
* Requires admin/root/CAP_* in typical deployments: -2. Reliable triggering usually requires watchdog device unregister, driver unbind, module unload, device removal, or power-management control.
* Availability impact realistic: +1. Suspend/resume after stale notifier registration can plausibly crash the kernel.
* Rare and difficult lifecycle condition: +1 not awarded. The condition is specific, but not rare enough for a strong negative because watchdog unregister plus PM notification is a normal kernel lifecycle path.

Paranoid additional signals:

* Memory corruption, weak/indirect corruption candidate: +1. The stale notifier implies a stale object pointer and possible UAF if the containing watchdog_device or driver object is freed and reused.
* Weak LPE concern: +1. The bug has a stale callback/lifetime shape, but no demonstrated reclaim, overwrite, or controlled replacement primitive is shown.
* Local unprivileged or reduced-privilege trigger concern: +1. Some systems may delegate suspend, hotplug, device unbind, or service-controlled power management to reduced local accounts rather than full host root.
* Hard or special sequencing required: -1. Practical triggering requires a specific sequence: unregister watchdog, keep stale PM notifier, then suspend/resume.

## 3. Reachability analysis

The bug is local, not network reachable. In typical deployments, triggering requires administrative control over watchdog lifecycle or power-management events, so conservative reachability is privileged local. Namespace or container impact is limited unless a container root, service account, or delegated management interface can trigger driver unbind, device removal, or suspend/resume. The affected path is not a common unprivileged syscall path, but it is a real kernel lifetime-management path involving global PM notifier callbacks.

Call-site confidence: high. The patch directly shows unregister_pm_notifier() being added before watchdog_dev_unregister(), and the commit message explains the stale notifier callback after teardown.

## 4. Severity interpretation

This is stronger than an ordinary cleanup bug because it leaves a notifier callback registered past the lifetime of the object it refers to. Realistically, the most likely impact is local DoS via kernel crash during suspend/resume. Theoretical memory-corruption potential exists because the notifier block is embedded in an object that may be freed or partially torn down, but the patch does not demonstrate attacker-controlled reclaim, object replacement, arbitrary write, or a reliable LPE primitive. Therefore this is best treated as Actionable Moderate at minimum, with manual review required, but not automatically a Strong Important candidate without more exploitability evidence.

## 5. One-sentence report phrase

A stale PM notifier can remain registered after watchdog device unregister, allowing a later suspend or resume event to call watchdog_pm_notifier on a torn down watchdog_device and causing at least a local kernel crash, with a defensible worst case UAF concern.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED

Reason: stale notifier lifetime bugs can become UAF callback paths after object teardown, and this case should not be auto-closed even though the conservative trigger normally requires privileged local lifecycle control.

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

Patch: watchdog: unregister PM notifier on watchdog unregister [ Upstream
Commit: cd2d1b1f99308f7680d75a377daaff363f1cc736
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=cd2d1b1f99308f7680d75a377daaff363f1cc736

Changed files:
  drivers/watchdog/watchdog_core.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=cd2d1b1f99308f7680d75a377daaff363f1cc736

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

The original Linux kernel CVE announcement for CVE-2026-74329 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74329

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:H/I:H/A:H
  The Best / paranoid CVSS score: 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: 2
  Paranoid ActionableScore: 5

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: NO
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).