[CVE-2026-98434][LOW] sysctl: Check range in proc_dointvec_ms_jiffies_minmax [ Upstream

[CVE-2026-98434][LOW] sysctl: Check range in proc_dointvec_ms_jiffies_minmax [ Upstream

[AL-KERNEL]

CVE: CVE-2026-98434
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: sysctl: Check range in proc_dointvec_ms_jiffies_minmax [ Upstream
Commit: 1c23dba51dbf7e86c7c2e617c964be1411329cb4
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=1c23dba51dbf7e86c7c2e617c964be1411329cb4
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98434
Analysis date: Mon, 19 Oct 2026 00:03:42 -0400
ActionableScore: 0
ActionableScore lower bound: unknown
Actionable bucket: Ordinary Moderate
Manual review required: NO

Summary:
A regression disabled minimum and maximum validation for millisecond based sysctl values, allowing an authorized writer to install an out of range timer setting without establishing memory corruption, authorization bypass, or a reliable denial of service.

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

The original Linux kernel CVE announcement for CVE-2026-98434 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98434

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-2026-98434	LOW	https://www.kernelcve.org/list/?q=CVE-2026-98434 CHECK WITH IMPACT FROM ORIG NN LOW | AEGIS IMPACT LOW AEGIS_AS=0 LEGACY=LOW RESULT=SAME (final reconciliation agrees; DECISION: both 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:L/A:L';*CWE-20;CWE-1284;CWE-682;Other CVSS 'AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:L/A:L';BEST CVSS score: '4.4';DESCR 'A regression in proc_dointvec_ms_jiffies_minmax disabled the configured minimum and maximum checks for sysctl values converted from milliseconds to jiffies. An authorized writer could therefore install an out of range timer value and bypass the limits defined by the affected sysctl table. The exact operational effect depends on the sysctl consumer, but plausible consequences include incorrect timer behavior, policy violation, and limited service degradation. For the CVSS the PR:L value is used for the paranoid score because a restricted service, container root, or namespace administrator may be delegated access to a writable affected sysctl without having full host administration rights. The issue is local and is not directly reachable through network traffic. No UAF, OOB access, information disclosure, arbitrary write, or other concrete memory corruption primitive is established by this code path. Automated impact decision path. The original SimpleNet classifier selected LOW. The primary LLM estimated paranoid CVSS 4.4 and the production ActionableScore returned 0 with recommendation Ordinary Moderate. The production rules then evaluated CVSS thresholds and ActionableScore thresholds. No severity changing production threshold or specialist override was recorded. 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. The independent weaker Aegis shadow evaluated CVSS 0.0 and ActionableScore 0 with primitive class NONE and manual review NO. Its independently reconciled impact was LOW. The shadow agreed with the final production impact and aggregation did not change that impact. The final reported impact is LOW.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 0)	MAYBE	SIMPLEFIX IMPROVEONLY 	-	-	checked

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

ActionableScore=0
PrimitiveClass=NONE
RealUAF=NO
HostAdminRequired=UNKNOWN
NamespaceScopedPrivilege=UNKNOWN
ImportantCandidate=NO
ManualReview=NO
AutoDowngradeAllowed=YES
RequiresHostUID0=UNKNOWN
AuthorizationDecisionBypass=NO
ProtectedResourceImpact=NONE
B4PendingReview=NO
B4PendingConfirmed=NO

1. ActionableScore

* Raw conservative score: 0
* Conservative score: 0
* Raw paranoid score: 0
* Paranoid score: 0
* No floor or cap changed either score.
* Final recommended bucket: **Ordinary Moderate**::

2. Signal breakdown

* +0 Validation defect. The handler passed `false` to `proc_int_conv()`, disabling the intended minimum and maximum checks.
* +0 Weak corruption concern. An authorized writer can install an out-of-range timer value, but this is an ordinary invalid value rather than kernel memory corruption.
* +0 Availability. No crash, stall, resource exhaustion, or host-wide failure is established.
* +0 Integrity. The writer already needs permission to modify the sysctl, and the missing range check is not shown to bypass an authorization boundary protecting another principal.
* No UAF, OOB read or write, refcount error, stale object, information disclosure, arbitrary write, or controlled corruption is established.
* No remote or ordinary local unprivileged trigger is established because affected sysctl table entries and permissions are not supplied.
* V33 and V32 do not apply because there is no corrupted active structured state or checksum metadata.
* B5-R does not apply because no heap OOB write, retry accumulation, or later consumption of corrupted descriptors exists.
* B3-PENDING does not apply because no shared-backing write exists.
* B4-PENDING does not apply because this is value-range validation, not a mandatory authorization DENY-to-ALLOW decision.

3. Reachability analysis

The operation is reachable only through a writable sysctl entry using `proc_dointvec_ms_jiffies_minmax()`. The supplied patch does not identify those entries, their modes, their governing user namespace, or whether they are writable through a network namespace.

Host-admin privilege is therefore not positively established, but neither is below-host-admin reachability. `HostAdminRequired` and `NamespaceScopedPrivilege` remain `UNKNOWN`. No network trigger, special hardware, race, or retry sequence is involved. Any availability consequence depends on an omitted call site accepting an out-of-range timer value and using it adversely.

4. Primitive and severity interpretation

The exact defect is failure to enforce the `extra1` and `extra2` bounds while converting a millisecond sysctl value to jiffies. The patch restores the existing range-validation mechanism by changing the `proc_int_conv()` range-check argument from `false` to `true`.

This does not establish memory corruption, lifetime corruption, authorization bypass, protected-resource access, or a reliable denial of service. The result is therefore `PrimitiveClass=NONE`. Stronger consequences remain unsupported without a concrete affected sysctl consumer and an adverse use of the invalid value.

`ImportantCandidate=NO` because no Important-preserving primitive exists. `AutoDowngradeAllowed=YES` because no unresolved corruption or security-boundary mechanism would be lost through automatic low-priority handling.

5. One-sentence report phrase

A regression disabled minimum and maximum validation for millisecond based sysctl values, allowing an authorized writer to install an out of range timer setting without establishing memory corruption, authorization bypass, or a reliable denial of service.

6. Manual review recommendation

NO MANUAL CHECK NEEDED

The patch is a validation-only correction with no demonstrated memory-safety, authorization, cross-boundary, or strong availability consequence. Reconsider only if a separate call-site analysis shows that a below-host-admin writer can use a specific affected sysctl to cause a security-relevant failure.

7. Call-site confidence

Call-site confidence: low

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

Patch: sysctl: Check range in proc_dointvec_ms_jiffies_minmax [ Upstream
Commit: 1c23dba51dbf7e86c7c2e617c964be1411329cb4
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=1c23dba51dbf7e86c7c2e617c964be1411329cb4

Changed files:
  kernel/time/jiffies.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=1c23dba51dbf7e86c7c2e617c964be1411329cb4

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

The original Linux kernel CVE announcement for CVE-2026-98434 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98434

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:L/PR:H/UI:N/S:U/C:N/I:L/A:L
  The Best / paranoid CVSS vector: AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:L
  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: 0

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).