[CVE-2026-90013][MODERATE 7.0] tracing: Take trace_array reference when opening options file [ Upstream

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

CVE: CVE-2026-90013
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: tracing: Take trace_array reference when opening options file [ Upstream
Commit: d0f37d77b9b4b241e0b30ef2562f6353cbda3bec
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=d0f37d77b9b4b241e0b30ef2562f6353cbda3bec
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90013
Analysis date: Wed, 16 Sep 2026 13:24:23 -0400
ActionableScore: 5
ActionableScore lower bound: unknown
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-2026-90013 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90013

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-2026-90013	MODERATE	https://www.kernelcve.org/list/?q=CVE-2026-90013 CHECK WITH IMPACT FROM ORIG NN IMPORTANT	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-416;CWE-362;*CWE-664;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '7';DESCR 'A race in tracefs options handling can cause a use-after-free because opening an options file did not take a reference on the related trace_array. One local task can keep an options file open while another task removes the tracing instance, leaving a stale trace_flags_index pointer that may later be used by read, write, or release paths. For the CVSS the PR:L is used for the paranoid score because some deployments delegate tracing controls to a less privileged local user, container root, or service account even though default systems usually restrict this to administrators. The issue is not network reachable and requires local access to tracefs control paths. Impact is at least local denial of service via kernel crash and in worst case may allow confidentiality or integrity impact due to use-after-free memory corruption, so manual review is recommended.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate / Strong Important candidate requiring manual review (with actual score 5)	YES	OOB INIT TRACE UAF KERNEL_PANIC_PLUS_UAF LINUS BOOT KPANIC  KPANIC DECREASED_TO_MODERATE70_BASED_ON_ACTIONABLESCORELOWERTHAN6	NO	NO	checked

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

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

1. ActionableScore

* Raw conservative score: 4
* Conservative score: 5
* Applied conservative floor: REAL UAF FLOOR 5 applies because the stale trace_array related pointer is used beyond a simple cleanup fault in tracefs option read/write handling, and host-admin-equivalent reachability is not positively established from the supplied evidence.
* Raw paranoid score: 5
* Paranoid score: 5
* Applied paranoid floor/cap: none
* Final recommended bucket: **Actionable Moderate / Strong Important candidate requiring manual review**::

2. Signal breakdown

Positive signals:

* +2 Real UAF / active lifetime violation: opening a tracefs options file did not take a trace_array reference, so instance removal can free the trace_array/options data while the opened file still uses inode->i_private / trace_flags_index.
* +1 Reliable kernel crash / strong DoS: the commit explicitly states that this can cause a use-after-free kernel crash.
* +1 Structured stale-object exploitation leverage: the stale trace_flags_index pointer is not merely a passive cleanup pointer. It is read to obtain an option index and used to recover the trace_array descriptor for option read/write operations.
* +1 Paranoid attacker-influenced lifetime manipulation: the same actor with sufficient tracefs control may keep an option file open and remove the tracing instance, repeatedly driving the lifetime transition. This is not counted in the conservative score because below-host-admin reachability is not proven.

Negative or non-awarded signals:

* 0 Controlled reclaim not demonstrated: no evidence shows attacker-controlled replacement contents at the freed trace_array address.
* 0 Arbitrary write not demonstrated: stale tracefs option write behavior is concerning, but a directed kernel write primitive is not established.
* 0 Confidentiality and integrity bonuses not awarded: C/I impact is plausible enough for manual review, but not independently established as a concrete disclosure or unauthorized modification primitive.
* 0 Remote reachability not established: this is a local tracefs control path, not packet-triggered or network reachable.
* 0 Concrete repeated release/refcount signal not awarded: the patch adds trace_array_put on release after a successful new reference acquisition. The vulnerable old path is missing get/put lifetime protection, not a visible second put on the exact same dangling reference.
* 0 Weak LPE not separately awarded: possible LPE is unresolved UAF leverage, not an established primitive.
* 0 Extra availability not awarded: the same kernel crash is already counted once.
* 0 Race penalty not applied: the bug involves concurrency, but the stale lifetime can persist after open and removal. This is not shown as a narrow one-shot timing race.
* 0 Host-admin penalty not applied: tracefs is commonly restricted, but the supplied evidence does not positively establish that the complete vulnerable operation requires host-admin-equivalent privilege in all relevant deployments.

Repeated-release/refcount checklist:

* First release can end lifetime: instance removal can free the trace_array/options data.
* Exact same reference survives: the opened file can retain the stale tr_index pointer.
* Second operation is a real lifetime/refcount mutation: no, the vulnerable old path is not shown to perform a second put/free on the same dangling reference.
* +1 Concrete repeated release/refcount awarded: no.
* Paranoid repeated-refcount leverage +1 awarded: no.
* FLOOR 5 applied: yes, but due active structured stale use in read/write paths, not due repeated release/refcount.

3. Reachability analysis

The trigger is local through tracefs. One task opens an options file for a tracing instance, while another task removes that instance. The complete operation likely requires permissions to access tracefs options and remove tracing instances, which are often limited to root or tracing administrators, but the supplied evidence does not prove a host-admin-equivalent requirement as an invariant.

HostAdminRequired is therefore UNKNOWN. NamespaceScopedPrivilege is NO because tracefs tracing instances are not shown to be user-namespace or network-namespace scoped. No network trigger is established. No special hardware is required. A prior tracefs mount or enabled tracing infrastructure may be needed in practice, but that is normal tracing subsystem exposure rather than rare hardware.

The race is practically repeatable by a local actor who can perform both open and instance removal. It is not merely a single narrow interrupt window.

4. Primitive and severity interpretation

The exact primitive is a real use-after-free / stale lifetime bug involving trace_array option state. The stale storage is an active structured kernel object, not a fixed DMA buffer or passive stale allocation. The stale pointer is used to derive option index and trace_array context for tracefs option operations.

This is not an ordinary stale cleanup dereference only. However, it is also not a proven CLASS_A primitive because controlled reclaim, attacker-shaped replacement contents, arbitrary kernel read/write, callback control, or demonstrated privilege escalation are not established.

PrimitiveClass is CLASS_B. The demonstrated consequence is local kernel crash / DoS. The speculative consequence is broader memory corruption impact from stale structured trace_array use, especially through read/write option paths after the instance has been removed. ImportantCandidate is YES because the active structured UAF has unresolved exploitation leverage beyond a pure immediate fault. AutoDowngradeAllowed is NO because automatically treating this as ordinary crash-only cleanup would discard a concrete unresolved kernel lifetime primitive.

Likely operational severity is Actionable Moderate at minimum, with Important-vs-Moderate review required.

5. One-sentence report phrase

A race in tracefs options handling can leave an opened options file with a stale trace_array option pointer after instance removal, causing a real UAF that can crash the kernel and requires manual review for possible impact beyond DoS.

6. Manual review recommendation

MANUAL CHECK REQUIRED

Reason: real active-object UAF is established, the stale pointer is used in tracefs option read/write logic, and exploitation leverage beyond crash is unresolved even though controlled reclaim or LPE is not demonstrated.

7. Call-site confidence

Call-site confidence: high

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

Patch: tracing: Take trace_array reference when opening options file [ Upstream
Commit: d0f37d77b9b4b241e0b30ef2562f6353cbda3bec
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=d0f37d77b9b4b241e0b30ef2562f6353cbda3bec

Changed files:
  kernel/20260828135858.2AC501F000E9
  kernel/trace/trace.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=d0f37d77b9b4b241e0b30ef2562f6353cbda3bec

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

The original Linux kernel CVE announcement for CVE-2026-90013 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90013

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: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: unknown
  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).