* [CVE-2026-98398][LOW] locking/lockdep: Invalidate stale class_cache entries for zapped classes [ Upstream
@ 2026-10-15 3:09 21% AL-KERNEL
0 siblings, 0 replies; 1+ results
From: AL-KERNEL @ 2026-10-15 3:09 UTC (permalink / raw)
To: kernel-cve
CVE: CVE-2026-98398
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: locking/lockdep: Invalidate stale class_cache entries for zapped classes [ Upstream
Commit: f8a1281ab82df5b51fd0384354d4b21daf2b7af0
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=f8a1281ab82df5b51fd0384354d4b21daf2b7af0
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98398
Analysis date: Wed, 14 Oct 2026 23:09:26 -0400
ActionableScore: 0
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-2026-98398 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98398
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-2026-98398 LOW https://www.kernelcve.org/list/?q=CVE-2026-98398 CHECK WITH IMPACT FROM ORIG NN LOW | AEGIS IMPACT LOW AEGIS_AS=0 LEGACY=LOW RESULT=SAME (legacy and Aegis reconciliation agree; DECISION: both 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-672;CWE-362;*CWE-664;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '4.1';DESCR 'A stale lockdep class_cache entry can remain after its lock class is zapped and can later refer to an inactive class slot or to an unrelated class that reused the same slot. This can produce an invalid class index, trigger a lockdep warning, or incorrectly associate a lock with another class through an ABA condition. The demonstrated primitive is stale diagnostic metadata rather than a freed memory dereference, out of bounds access, or arbitrary write. For the CVSS the PR:H value is used because reliably creating the stale state normally requires administrative operations such as module unloading or lock key unregistration. The WireGuard workqueue and network stack can expose the stale entry after it exists, but the patch does not establish an independent remote network trigger. Impact is normally limited to incorrect lock dependency diagnostics and a warning. Availability impact can become higher on systems configured to panic on warnings, while confidentiality and integrity impact are not supported by the code path. Automated impact decision path. The original SimpleNet classifier selected MODERATE_KPANIC. The primary LLM estimated paranoid CVSS 4.1 and the production ActionableScore returned 0 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. final reconciliation stage LOW to LOW because KP specialist did not establish a qualifying panic. 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 and KPANIC_UNSUPPORTED_REMOVED. The independent weaker Aegis shadow evaluated CVSS 0.0 and ActionableScore 0 with primitive class CLASS_C 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 OOB LOCK DANGER HARDWARE LINUS SYZBOT DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3 KPANIC_UNSUPPORTED_REMOVED - - checked
======================================================================
ACTIONABLESCORE ANALYSIS
======================================================================
ActionableScore=0
PrimitiveClass=CLASS_C
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 was applied.
* Final recommended bucket: **Ordinary Moderate**::
2. Signal breakdown
* +0 stale diagnostic metadata: `class_cache[]` can retain a pointer to a logically retired lock class, but the pointer remains within the static `lock_classes` array.
* +0 WARN: the demonstrated result is a lockdep warning caused by an invalid `class_idx`. `WARN_ON` alone does not receive a crash point.
* +0 ABA diagnostic mismatch: slot reuse can associate a lock with an unrelated class, but this corrupts lockdep analysis rather than an active security object.
* No UAF signal: no freed heap object is dereferenced. Zapping retires a lock class and marks its array slot unused, but does not free the underlying `lock_classes` storage.
* No OOB read or write, arbitrary write, controlled reclaim, refcount mutation, callback control, disclosure, or authorization bypass is established.
* No crash point: panic would depend on an additional configuration such as `panic_on_warn`, which is not established by the supplied evidence.
* No remote-reachability point: the WireGuard workqueue is where the stale entry was observed, not evidence that network traffic alone can create the stale cache state.
* B5-R is not applicable. There is no heap OOB write, retry-accumulated offset, or later consumption of corrupted heap contents.
* B3-PENDING is not applicable. No shared-backing write exists.
* B4-PENDING is not applicable. No mandatory authorization guard changes from DENY to ALLOW.
3. Reachability analysis
The observed warning occurs when a lock using a stale cached class is acquired after the class has been zapped. Module unloading and key unregistration are given as examples of class retirement, but the supplied diff does not establish that every complete trigger requires host-admin-equivalent privilege. Therefore `HostAdminRequired` remains `UNKNOWN` rather than assuming either privileged or below-admin reachability.
The WireGuard transmit worker and TCP path merely expose the stale lockdep entry after it exists. They do not establish a direct remote trigger for class zapping or cache invalidation failure. No complete namespace-scoped trigger, attacker-created namespace path, prior setup requirement, special hardware requirement, or repeatable attacker-controlled race is demonstrated.
4. Primitive and severity interpretation
The exact defect is stale lockdep cache metadata. A `lockdep_map` can retain a pointer to a lock-class array slot after that class is removed from the active bitmap and hash table. Reuse of the slot can create an ABA mismatch, but the stale pointer does not reference freed allocation storage.
This is neither active structured-object UAF nor fixed stale storage UAF. There is no concrete repeated release or refcount operation. The affected state is diagnostic lock dependency metadata, and the demonstrated consequence is a warning or incorrect lockdep classification.
`PrimitiveClass=CLASS_C` is appropriate because the behavior is invalid-state and warning oriented without an independently useful corruption primitive. `ImportantCandidate=NO` and `AutoDowngradeAllowed=YES` follow because no memory-corruption, ownership, authorization, confidentiality, integrity, or unresolved lifetime-mutation primitive remains.
5. One-sentence report phrase
A stale lockdep class cache entry can reference a retired or reassigned class slot and trigger warnings or incorrect dependency diagnostics, but the patch does not establish a real UAF, memory corruption, authorization bypass, or independently useful exploitation primitive.
6. Manual review recommendation
NO MANUAL CHECK NEEDED
The issue is confined to stale diagnostic metadata, with no demonstrated security primitive beyond a lockdep warning and possible diagnostic misclassification.
7. Call-site confidence
Call-site confidence: medium
======================================================================
UPSTREAM PATCH SUMMARY
======================================================================
Patch: locking/lockdep: Invalidate stale class_cache entries for zapped classes [ Upstream
Commit: f8a1281ab82df5b51fd0384354d4b21daf2b7af0
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=f8a1281ab82df5b51fd0384354d4b21daf2b7af0
Changed files:
kernel/locking/lockdep.c
kernel/locking/spinlock.c
net/ipv4/tcp_output.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=f8a1281ab82df5b51fd0384354d4b21daf2b7af0
======================================================================
DETAILED REPORT METHODOLOGY
======================================================================
The original Linux kernel CVE announcement for CVE-2026-98398 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98398
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:L
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: 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 [email protected] (and both
send reply to CVE record itself too and see "reply" button below for howto reply).
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