[CVE-2026-98147][LOW] printk: Don't WARN on kthread_run failure. [ Upstream

[CVE-2026-98147][LOW] printk: Don't WARN on kthread_run failure. [ Upstream

[AL-KERNEL]

CVE: CVE-2026-98147
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: printk: Don't WARN on kthread_run failure. [ Upstream
Commit: 4e676279798148382497d0e38c0bd51115e64be1
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=4e676279798148382497d0e38c0bd51115e64be1
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98147
Analysis date: Fri, 25 Sep 2026 15:26:32 -0400
ActionableScore: 1
ActionableScore lower bound: 0
Actionable bucket: Ordinary Moderate
Manual review required: NO

Summary:
No one-sentence report phrase was found.

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

The original Linux kernel CVE announcement for CVE-2026-98147 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98147

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-2026-98147	LOW	https://www.kernelcve.org/list/?q=CVE-2026-98147 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:H/UI:N/S:U/C:N/I:N/A:H';CWE-617;CWE-703;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:N';BEST CVSS score: '4.1';DESCR 'The printk console setup path used WARN_ON when kthread_run returned an error even though EINTR is an expected result when the waiting task receives SIGKILL. Under a normal kernel configuration this produces a diagnostic warning and stack trace without memory corruption or a direct confidentiality integrity or availability impact. On systems configured with panic_on_warn the same condition can cause a kernel panic and local denial of service. For the CVSS the PR:H value is used because reliable triggering normally requires administrative control over console related setup and the ability to deliver SIGKILL to the relevant privileged task. AC:H reflects the required timing between printer thread creation and signal delivery. The issue is not network reachable and there is no UAF OOB access information leak arbitrary write or plausible privilege escalation primitive.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 1)  SKIP CVE-2026-98147 UNKNOWN SKIP The Fixes patch not applied yet, so unlikely that actual: url YES  NO NO unknown 	MAYBE	WARNONLY SIMPLEFIX LINUS SYZBOT 	-	-	checked

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

ActionableScore=1
ActionableScoreLower=0
PrimitiveClass=CLASS_C
RealUAF=NO
HostAdminRequired=UNKNOWN
NamespaceScopedPrivilege=UNKNOWN
ImportantCandidate=NO
ManualReview=NO
AutoDowngradeAllowed=YES

1. ActionableScore

* Raw conservative score: 0
* Conservative score: 0
* Raw paranoid score: 1
* Paranoid score: 1
* No floor or cap was applied.
* Final recommended bucket: **Ordinary Moderate**::

2. Signal breakdown

Conservative:

* +0 Expected `kthread_run()` failure produces only an unnecessary `WARN_ON`, diagnostic stack trace, and normal error return.
* +0 No UAF, OOB access, overwrite, stale object, refcount error, disclosure, or authorization bypass is established.
* +0 `WARN_ON` alone is not counted as a fatal availability impact.

Paranoid:

* +1 Reliable kernel crash or strong DoS under the specific `panic_on_warn` configuration, where the reachable warning becomes fatal.

Not awarded:

* No remote-reachability point.
* No local-unprivileged point because the complete console setup and signal-control path is not established below host administration.
* No corruption or exploitation-leverage point.
* No additional availability point because it would duplicate the same conditional panic.
* No timing penalty. Although SIGKILL must arrive while thread creation is waiting, the evidence does not establish that this timing is materially uncontrollable.
* No configuration penalty. `panic_on_warn` is a prerequisite for the paranoid impact, but rarity is not sufficiently established for subtraction.

3. Reachability analysis

The condition occurs when `kthread_run()` returns `-EINTR` because the task waiting in `__kthread_create_on_node()` receives `SIGKILL`. The supplied context suggests that reliable triggering normally involves console-related setup and control over the relevant privileged task, but it does not expose enough call-site or capability-check detail to positively establish host-admin equivalence. Therefore `HostAdminRequired=UNKNOWN`, and no privilege penalty is applied.

No namespace-scoped trigger chain, network path, remote input, special hardware dependency, or ordinary-user interface is established. The trigger requires a specific signal ordering, but this is an expected interruption path rather than a demonstrated difficult race.

4. Primitive and severity interpretation

The exact defect is inappropriate assertion behavior on an expected error return. The error is already detected through `IS_ERR()`, and both paths return failure without using the error pointer as a valid task.

There is no stale storage, active structured UAF, repeated release, refcount mutation, or memory corruption. The demonstrated normal consequence is a warning and stack trace. The paranoid consequence is kernel panic only when `panic_on_warn` converts that warning into a fatal event.

This is `CLASS_C` because the only security-relevant consequence is conditional crash or DoS behavior. There is no leverage beyond that crash, so it is not an Important candidate and automatic downgrade is allowed.

5. One-sentence report phrase

An expected `kthread_run()` interruption can reach `WARN_ON` during printk printer-thread creation and can cause a local kernel panic only on systems configured with `panic_on_warn`, with no evidence of memory corruption, information disclosure, privilege escalation, or network reachability.

6. Manual review recommendation

NO MANUAL CHECK NEEDED

The patch removes a nonessential warning from an already handled error path, and no unresolved corruption or security-boundary primitive remains.

7. Call-site confidence

Call-site confidence: medium

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

Patch: printk: Don't WARN on kthread_run failure. [ Upstream
Commit: 4e676279798148382497d0e38c0bd51115e64be1
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=4e676279798148382497d0e38c0bd51115e64be1

Changed files:
  kernel/printk/nbcon.c
  kernel/printk/printk.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=4e676279798148382497d0e38c0bd51115e64be1

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

The original Linux kernel CVE announcement for CVE-2026-98147 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98147

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:N
  The Best / paranoid CVSS vector: AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS score: 4.1

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).