* [CVE-2026-97443][LOW] perf/ftrace: Fix WARNING in __unregister_ftrace_function [ Upstream
@ 2026-09-25 0:25 21% AL-KERNEL
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From: AL-KERNEL @ 2026-09-25 0:25 UTC (permalink / raw)
To: kernel-cve
CVE: CVE-2026-97443
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: perf/ftrace: Fix WARNING in __unregister_ftrace_function [ Upstream
Commit: df097713b56ffac5eed32a9be2e7d27ac48d9087
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=df097713b56ffac5eed32a9be2e7d27ac48d9087
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-97443
Analysis date: Thu, 24 Sep 2026 20:25:09 -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-2026-97443 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-97443
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-2026-97443 LOW https://www.kernelcve.org/list/?q=CVE-2026-97443 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:L/UI:N/S:U/C:N/I:N/A:L';CWE-754;CWE-703;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:N';BEST CVSS score: '2.5';DESCR 'A perf event cleanup path can call unregister_ftrace_function for an ftrace_ops object that was never successfully registered or was already disabled. This triggers a kernel WARN because the FTRACE_OPS_FL_ENABLED flag is not set. For the CVSS the PR:L because a local process must be able to create the relevant perf tracing event and reach a specific registration failure or cleanup path. The issue is not network reachable. The available evidence indicates kernel warning and log noise only, without a memory safety primitive, privilege escalation, information disclosure, or direct system crash.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 0) YES INIT WARNONLY TRACE LINUS NO NO checked
======================================================================
ACTIONABLESCORE ANALYSIS
======================================================================
ActionableScore=0
PrimitiveClass=NONE
RealUAF=NO
HostAdminRequired=UNKNOWN
NamespaceScopedPrivilege=UNKNOWN
ImportantCandidate=NO
ManualReview=NO
AutoDowngradeAllowed=YES
1. ActionableScore
* Raw conservative score: 0
* Conservative score: 0
* Raw paranoid score: 0
* Paranoid score: 0
* Final recommended bucket: **Ordinary Moderate**::
The supplied patch establishes a WARN_ON-only cleanup-state mismatch. No score-changing security primitive or availability consequence is established.
2. Signal breakdown
* +0 WARN_ON only. Calling unregister_ftrace_function on an ftrace_ops without FTRACE_OPS_FL_ENABLED triggers a kernel warning.
* +0 No memory corruption. The patch does not establish UAF, double free, refcount mutation, stale dereference, OOB access, invalid free, or active-object lifetime violation.
* +0 No reliable kernel crash or strong DoS. A WARN_ON and kernel log entry are established, but panic behavior is configuration dependent and not demonstrated.
* +0 No confidentiality or integrity impact. There is no disclosure, unauthorized modification, authorization bypass, or privilege escalation primitive.
* +0 No remote reachability. The affected path is reached through local perf event allocation and cleanup.
* +0 No local-unprivileged trigger bonus. The supplied evidence does not establish that an ordinary unprivileged user can create the required trace perf event and reliably reach the failed registration cleanup path.
* No privilege penalty applied. The complete perf tracing permission boundary is not resolved by the patch, so host-admin-equivalent privilege cannot be positively asserted.
* No race penalty applied. This is an ordered registration failure and cleanup sequence, not a demonstrated timing race.
3. Reachability analysis
The affected path is local. It requires perf_event_alloc to create a trace perf event, followed by a failure or prior teardown of ftrace_ops registration, then event destruction through the perf cleanup path.
The patch does not establish whether the complete trigger is available to an ordinary unprivileged user, a user with delegated perf tracing access, or only an administrator under a restrictive perf_event_paranoid policy. Therefore HostAdminRequired is UNKNOWN.
No network namespace, user namespace, or namespace-scoped capability facts are supplied. NamespaceScopedPrivilege is UNKNOWN. No special hardware, device setup, boot option, or remote input is involved.
4. Primitive and severity interpretation
The exact defect is an invalid cleanup-state operation. perf_ftrace_function_unregister unconditionally calls unregister_ftrace_function even when the ftrace_ops object was never registered or has already been disabled.
This is not a UAF. The affected ftrace_ops is embedded in struct perf_event, and the visible patch does not show that its storage has been freed, that an old reference survives object destruction, or that unregister performs a second lifetime-affecting operation on freed storage. The checked FTRACE_OPS_FL_ENABLED flag represents registration state, not proof of an object-lifetime violation.
The demonstrated consequence is a WARN_ON in __unregister_ftrace_function and associated kernel log noise. A crash, persistent DoS, information disclosure, integrity impact, controlled corruption, or privilege escalation is not established. The primitive class is NONE. ImportantCandidate is NO and AutoDowngradeAllowed is YES because no unresolved kernel-corruption or security-boundary primitive remains.
5. One-sentence report phrase
A perf event cleanup path can invoke unregister_ftrace_function for an ftrace_ops object that is not enabled, causing a kernel WARN without an established memory-safety or security impact.
6. Manual review recommendation
NO MANUAL CHECK NEEDED
The patch fixes a WARN-only invalid-state cleanup path, with no demonstrated UAF, corruption, crash, authorization bypass, or remotely reachable trigger.
7. Call-site confidence
Call-site confidence: high
======================================================================
UPSTREAM PATCH SUMMARY
======================================================================
Patch: perf/ftrace: Fix WARNING in __unregister_ftrace_function [ Upstream
Commit: df097713b56ffac5eed32a9be2e7d27ac48d9087
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=df097713b56ffac5eed32a9be2e7d27ac48d9087
Changed files:
kernel/trace/trace_event_perf.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=df097713b56ffac5eed32a9be2e7d27ac48d9087
======================================================================
DETAILED REPORT METHODOLOGY
======================================================================
The original Linux kernel CVE announcement for CVE-2026-97443 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-97443
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:L/UI:N/S:U/C:N/I:N/A:N
The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:L
The Best / paranoid CVSS score: 2.5
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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