[CVE-2026-98032][MODERATE 7.0] tracing: Fix subbuf resize races with trace_pipe_raw readers [ Upstream

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

CVE: CVE-2026-98032
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: tracing: Fix subbuf resize races with trace_pipe_raw readers [ Upstream
Commit: 75b37b8369778b69ce9738d1c97685a1615cb252
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=75b37b8369778b69ce9738d1c97685a1615cb252
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98032
Analysis date: Sat, 26 Sep 2026 03:06:16 -0400
ActionableScore: 5
ActionableScore lower bound: 3
Actionable bucket: Actionable Moderate / Strong Important candidate requiring manual review
Manual review required: YES

Summary:
No one-sentence report phrase was found.

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

The original Linux kernel CVE announcement for CVE-2026-98032 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98032

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-2026-98032	MODERATE	https://www.kernelcve.org/list/?q=CVE-2026-98032 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-362;*CWE-457;*CWE-787;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:H/I:N/A:H';BEST CVSS score: '7';DESCR 'A race between ring buffer subbuffer resizing and trace_pipe_raw reading can leave the reader using a page whose order and capacity no longer match the current subbuffer size. Stale size values can cause data to be copied or cleared using the wrong capacity, which may expose uninitialized kernel memory to userspace or access memory outside the destination page and crash the kernel. For the CVSS the PR:L value is used for the paranoid score because tracefs access can be delegated to a tracing group, container administrator, or restricted service account without granting complete host administration. The attack is local and requires a timing window between a privileged resize operation and a trace_pipe_raw read, so AC:H is appropriate. There is no direct network attack path. Impact includes kernel memory disclosure and denial of service, with possible integrity impact if the size mismatch results in an out of bounds write.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate / Strong Important candidate requiring manual review (with actual score 4)  SKIP CVE-2026-98032 UNKNOWN SKIP The Fixes patch not applied yet, so unlikely that actual: url YES  NO NO unknown 	MAYBE	READ DANGER INIT NOMEMCHK RACE UAF KERNEL_PANIC_PLUS_UAF HARDWARE LINUS KPANIC MEMORY 	-	-	checked

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

ActionableScore=5
ActionableScoreLower=3
PrimitiveClass=CLASS_B
RealUAF=NO
HostAdminRequired=UNKNOWN
NamespaceScopedPrivilege=NO
ImportantCandidate=YES
ManualReview=REQUIRED
AutoDowngradeAllowed=NO

1. ActionableScore

* Raw conservative score: 3
* Conservative score: 3
* Raw paranoid score: 5
* Paranoid score: 5
* No floor or cap was applied.
* Final recommended bucket: **Actionable Moderate / Strong Important candidate requiring manual review**::

2. Signal breakdown

Conservative signals:

* +1 Constrained kernel buffer overwrite. A stale order can make the reader page larger than `buffer_data_read_page`, while the old clearing and copying logic uses the reader capacity against the smaller destination. The resulting overwrite has a fixed zero or kernel-derived payload and no demonstrated target selection.
* +1 Confidentiality plausible. The commit explicitly establishes that stale size values can expose uninitialized kernel memory to userspace through `trace_pipe_raw`.
* +1 Reliable kernel crash or strong DoS. The commit explicitly states that concurrent resizing can crash readers, and the capacity mismatch supports an in-kernel out-of-bounds fault.
* Total: 3.

Additional paranoid signals:

* +1 Integrity plausible. The old `memset()` can use `rb_page_capacity(reader)` while writing through `data_page`; when the reader page is larger, this provides a technically defensible out-of-bounds zeroing mechanism beyond the destination allocation.
* +1 Weak exploitation concern. The configured subbuffer orders influence the size mismatch and possible overwrite extent, although neither the adjacent target nor useful replacement contents are shown.
* Total: 5.

Negative signals:

* No host-admin penalty. The complete permission boundary for concurrent resize and read is not visible, so host-admin-equivalent privilege is not positively established.
* No race penalty. The operations can potentially be repeated, and the evidence does not establish a narrow, one-shot, or externally uncontrollable timing window.
* No niche-subsystem penalty. The specific feature is specialized, but rarity and difficult reachability are not both established.

Material non-awarded signals:

* Controlled target selection, controlled reclaim, arbitrary write, callback control, and privilege escalation are not demonstrated.
* Strong corruption leverage was not awarded because the apparent overwrite is zero-filled, adjacent to a fixed read-page buffer, and lacks demonstrated target selection.
* No extra Availability point was awarded because the same crash is already counted.
* No Real UAF signal was awarded because the defect is a size/order race, not a demonstrated post-lifetime object use.
* Remote reachability is not established.
* The memory-layout invariant was not scored separately because it describes the same capacity mismatch already counted as the constrained overwrite.
* The direct disclosure is scored, but it is not classified as a substantial controlled kernel disclosure without evidence about exposed contents and repeatable selection.

3. Reachability analysis

The vulnerable sequence requires a `trace_pipe_raw` reader to overlap a ring-buffer subbuffer resize. Reading tracing data and changing buffer geometry are tracefs control operations, but the supplied call sites do not establish whether one below-host-admin principal can perform both operations. Tracefs files can be permission-delegated, but theoretical delegation is insufficient to prove below-host-admin reachability.

Therefore, `HostAdminRequired=UNKNOWN`. The operation is not made available by capabilities obtained in an attacker-created user or network namespace, so `NamespaceScopedPrivilege=NO`. No network trigger, special hardware, firmware dependency, or boot-only mode is required. The race appears repeatable through concurrent read and resize loops, so no hard-race reduction is justified.

4. Primitive and severity interpretation

The exact primitive is a race-induced disagreement between the allocated capacity of `buffer_data_read_page`, the current ring-buffer subbuffer order, and the capacity of the selected reader page. The old code could use a stale or mismatched larger size for copying, clearing, and userspace-visible length handling.

This establishes direct uninitialized-memory disclosure and a plausible constrained out-of-bounds zero write. It does not establish a UAF, controlled replacement object, arbitrary destination, or attacker-selected payload. The storage is an active read buffer, but there is no lifetime violation or repeated release/refcount mutation.

The issue is `CLASS_B` because a real kernel memory-boundary violation exists and exploitation leverage requires inspection, but the demonstrated mechanics remain weaker than Class A. The demonstrated consequences are information disclosure and crash/DoS. Integrity impact is the technically defensible paranoid consequence of the out-of-bounds clearing operation.

`ImportantCandidate=YES` because the combination of userspace-visible uninitialized kernel memory and a possible out-of-bounds kernel write requires Important-vs-Moderate review. `AutoDowngradeAllowed=NO` because automatic closure could discard a concrete disclosure and unresolved overwrite primitive. The likely operational severity is Actionable Moderate unless call-site analysis establishes useful adjacent-object corruption, broad disclosure, or a below-host-admin complete trigger.

5. One-sentence report phrase

A race between trace_pipe_raw reads and ring-buffer subbuffer resizing can apply stale page sizes to a differently sized destination, exposing uninitialized kernel memory and potentially causing an out-of-bounds zero write or kernel crash.

6. Manual review recommendation

MANUAL CHECK REQUIRED

Confirm the complete tracefs permission model, the maximum order mismatch, the exact old copy-loop bounds, whether the stale userspace length can read beyond the allocation, and which kernel allocations can follow an undersized read page.

7. Call-site confidence

Call-site confidence: medium

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

Patch: tracing: Fix subbuf resize races with trace_pipe_raw readers [ Upstream
Commit: 75b37b8369778b69ce9738d1c97685a1615cb252
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=75b37b8369778b69ce9738d1c97685a1615cb252

Changed files:
  include/linux/ring_buffer.h
  kernel/trace/ring_buffer.c
  kernel/trace/ring_buffer_benchmark.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=75b37b8369778b69ce9738d1c97685a1615cb252

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

The original Linux kernel CVE announcement for CVE-2026-98032 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98032

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:H/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: 3
  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: YES
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).