* [CVE-2026-98409][LOW] watchdog: rtd119x: Avoid division by zero
@ 2026-10-15 2:28 21% AL-KERNEL
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From: AL-KERNEL @ 2026-10-15 2:28 UTC (permalink / raw)
To: kernel-cve
CVE: CVE-2026-98409
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: watchdog: rtd119x: Avoid division by zero
Commit: 757c721545b9ffac5c3042a0cd3685ea28af7e81
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=757c721545b9ffac5c3042a0cd3685ea28af7e81
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98409
Analysis date: Wed, 14 Oct 2026 22:28:43 -0400
ActionableScore: 1
ActionableScore lower bound: unknown
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-2026-98409 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98409
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-2026-98409 LOW https://www.kernelcve.org/list/?q=CVE-2026-98409 CHECK WITH IMPACT FROM ORIG NN MODERATE | AEGIS IMPACT MODERATE_KPANIC AEGIS_AS=0 LEGACY=LOW RESULT=DIFF TEMP_DISTANCE_MERGE_SKIP=AEGIS_LOW_ELIGIBLE_NO_POSITIVE_SIGNAL (independent Legacy and Aegis differ; FINAL: LOW, Aegis: MODERATE_KPANIC) Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H';CWE-369;*CWE-20;CWE-754;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '4.4';DESCR 'The rtd119x watchdog driver can divide by zero during device probe when clk_get_rate returns 0 and that value is used to calculate max_timeout. The resulting kernel exception may cause a kernel panic and denial of service during driver initialization or device binding. For the CVSS the PR:H reflects that reliably reaching the condition normally requires administrative control over driver binding or platform clock configuration. The issue is not network reachable and an ordinary unprivileged local user is not shown to control the affected clock source. Impact is limited to availability because the code path provides no UAF OOB access information disclosure or write primitive. Automated impact decision path. The original SimpleNet classifier selected MODERATE_KPANIC. The primary LLM estimated paranoid CVSS 4.4 and the production ActionableScore returned 1 with recommendation Ordinary Moderate. The production rules then evaluated CVSS thresholds and ActionableScore thresholds. Recorded rule transitions were CVSS and initial triage stage MODERATE_KPANIC to MODERATE because the CVSS score, vector or bug class threshold rule was applied. ActionableScore thresholds stage MODERATE to LOW because the ActionableScore threshold rule was applied. The legacy KP specialist has no review artifact for this run. The legacy FD or DH downgrade specialist has no review artifact for this run. Exact triggered rule markers were DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS and DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3. The independent weaker Aegis shadow evaluated CVSS 4.2 and ActionableScore 0 with primitive class CLASS_C and manual review NO. Its independently reconciled impact was MODERATE_KPANIC. The models disagreed but the aggregation rules retained the production result. The final reported impact is LOW.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 1) MAYBE DANGER SIMPLEFIX HARDWARE LINUS DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3 - - checked
======================================================================
ACTIONABLESCORE ANALYSIS
======================================================================
ActionableScore=1
PrimitiveClass=CLASS_C
RealUAF=NO
HostAdminRequired=UNKNOWN
NamespaceScopedPrivilege=NO
ImportantCandidate=NO
ManualReview=NO
AutoDowngradeAllowed=YES
RequiresHostUID0=UNKNOWN
AuthorizationDecisionBypass=NO
ProtectedResourceImpact=NONE
B4PendingReview=NO
B4PendingConfirmed=NO
1. ActionableScore
* Raw conservative score: 1
* Conservative score: 1
* Raw paranoid score: 1
* Paranoid score: 1
* No floor or cap was applied.
* Final recommended bucket: **Ordinary Moderate**::
2. Signal breakdown
* +1 Reliable kernel crash / strong DoS: the commit explicitly identifies a division-by-zero panic when `clk_get_rate()` returns zero during `rtd119x_wdt_probe()`.
* No additional availability point: it would duplicate the same panic, and no persistent failure beyond ordinary recovery is established.
* No corruption point: the invalid arithmetic operation occurs before assignment to `max_timeout`; no OOB access, UAF, overwrite, stale object, or ownership violation exists.
* No local-unprivileged point: no ordinary-user interface capable of controlling the clock rate or initiating the complete vulnerable probe sequence is established.
* No privilege penalty: administrative control appears relevant to deliberate driver binding or clock reconfiguration, but the supplied evidence does not positively establish the complete attacker model.
* No rare-hardware penalty: the driver is hardware-specific, but the evidence does not establish physical attacker access or sufficiently rare hardware to justify subtraction.
* B5-R does not apply: there is no heap OOB write, retry accumulation, or later consumption of corrupted structured state.
* B3-PENDING does not apply: no shared backing or file-backed write exists.
* B4-PENDING does not apply: no authorization guard or DENY-to-ALLOW decision is involved.
3. Reachability analysis
The vulnerable operation runs during probe of the Realtek RTD119x or RTD1295 watchdog platform device. A zero rate can arise from invalid or unavailable platform clock state, after which the division occurs immediately.
No network, namespace, ioctl, or ordinary-user trigger is shown. Deliberately changing platform clock configuration or rebinding the driver would normally involve privileged device management, but the patch does not establish that these are the only ways the zero rate can occur. It may also occur automatically during boot or probe because of platform configuration. Therefore `HostAdminRequired` and `RequiresHostUID0` remain unknown rather than being inferred as either required or unnecessary.
The operation is not namespace-scoped. There is no race, retry sequence, prior attacker-created object, or attacker-controlled payload.
4. Primitive and severity interpretation
The exact primitive is an unchecked zero divisor in:
`0xffffffff / clk_get_rate(data->clk)`
The demonstrated consequence is a kernel arithmetic exception and possible panic. This is CLASS_C crash behavior, not memory corruption. There is no stale storage, active structured-object UAF, repeated release, refcount mutation, semantic reinterpretation, or security-boundary bypass.
No useful exploitation primitive remains after excluding the crash. Confidentiality, integrity, privilege escalation, and arbitrary kernel access are unsupported. The patch-supported practical impact is availability loss on an affected platform during driver probing.
`ImportantCandidate=NO` because neither a corruption primitive nor an authorization or ownership violation exists. `AutoDowngradeAllowed=YES` because the issue is a direct, bounded, hardware-specific arithmetic panic with no unresolved exploitation leverage.
5. One-sentence report phrase
The rtd119x watchdog probe can divide by zero when its clock reports a zero rate, causing a kernel panic without establishing memory corruption, authorization bypass, or a below-host-admin attacker path.
6. Manual review recommendation
NO MANUAL CHECK NEEDED
The root cause and consequence are direct and limited to a division-by-zero DoS, with no evidence of a stronger security primitive.
7. Call-site confidence
Call-site confidence: high
======================================================================
UPSTREAM PATCH SUMMARY
======================================================================
Patch: watchdog: rtd119x: Avoid division by zero
Commit: 757c721545b9ffac5c3042a0cd3685ea28af7e81
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=757c721545b9ffac5c3042a0cd3685ea28af7e81
Commit description:
clk_get_rate() could return 0. Avoid a division by zero panic.
Fixes: 2bdf6ac ("watchdog: Add Realtek RTD1295")
Cc: [email protected]
Signed-off-by: Tzung-Bi Shih <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Guenter Roeck <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
Changed files:
drivers/watchdog/rtd119x_wdt.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=757c721545b9ffac5c3042a0cd3685ea28af7e81
======================================================================
DETAILED REPORT METHODOLOGY
======================================================================
The original Linux kernel CVE announcement for CVE-2026-98409 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98409
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:L/PR:H/UI:N/S:U/C:N/I:N/A:H
The Best / paranoid CVSS score: 4.4
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: unknown
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 [email protected] (and both
send reply to CVE record itself too and see "reply" button below for howto reply).
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