[CVE-2026-90306][LOW] ARM: 9481/2: breakpoint: CFI breakpoints only on demand [ Upstream

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

CVE: CVE-2026-90306
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: ARM: 9481/2: breakpoint: CFI breakpoints only on demand [ Upstream
Commit: 22107402c2669b0163d43cc68901a2c4a59fa43a
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=22107402c2669b0163d43cc68901a2c4a59fa43a
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90306
Analysis date: Thu, 17 Sep 2026 22:49:44 -0400
ActionableScore: 1
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-2026-90306 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90306

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-2026-90306	LOW	https://www.kernelcve.org/list/?q=CVE-2026-90306 CHECK WITH IMPACT FROM ORIG NN MODERATE	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-755;CWE-754;CWE-693;Other CVSS 'AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '4.4';DESCR 'ARM breakpoint handling can incorrectly consume userspace breakpoint type 0x03 instead of returning an unhandled fault to the normal userspace exception path. When CONFIG_CFI is disabled the empty CFI handler treats the breakpoint as handled, while with CONFIG_CFI enabled the same breakpoint can also be intercepted when it originates from user mode. This may prevent a debugger, runtime, or application from receiving the expected breakpoint exception and can disrupt the affected process or alter its expected control flow. For the CVSS the PR:L is selected because triggering requires execution of local userspace code, although no administrative capability is required. The issue is not network reachable. Impact is limited to availability and potentially low integrity impact within the affected userspace execution context. There is no evidence of a UAF, OOB access, arbitrary write, information disclosure, kernel crash, or privilege escalation.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 1)  SKIP CVE-2026-90306 UNKNOWN SKIP The Fixes patch not applied yet, so unlikely that actual: url YES  NO NO unknown 	MAYBE	DANGER SIMPLEFIX HARDWARE  DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3	-	-	checked

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

ActionableScore=1
PrimitiveClass=NONE
RealUAF=NO
HostAdminRequired=NO
NamespaceScopedPrivilege=NO
ImportantCandidate=NO
ManualReview=NO
AutoDowngradeAllowed=YES

1. ActionableScore

* Raw conservative score: 1
* Conservative score: 1
* Raw paranoid score: 1
* Paranoid score: 1
* No floor or cap applied.
* Final recommended bucket: **Ordinary Moderate**::

2. Signal breakdown

* +1 Local unprivileged trigger. An ordinary ARM userspace process can execute breakpoint type 0x03 without administrative privileges.
* No kernel crash or strong DoS point. The demonstrated effect is failure to deliver the expected userspace exception, not a kernel panic.
* No corruption point. The patch establishes incorrect exception dispatch but no UAF, OOB access, stale object, overwrite, or lifetime violation.
* No integrity point. Altered control flow is confined to the process issuing the breakpoint, with no demonstrated unauthorized modification of another principal or protected kernel state.
* No confidentiality point. No disclosure path exists.
* No authorization-bypass point. No mandatory security check changes from deny to allow.
* No remote-reachability point. The operation requires local userspace execution.
* No negative privilege penalty. Below-host-admin reachability is positively established.
* No rarity penalty. ARM-specific code alone does not establish rare hardware or a difficult-to-reach configuration.
* The paranoid score is not increased because no additional technically defensible security primitive is established.

3. Reachability analysis

An ordinary local user can execute the affected BKPT instruction within a userspace process. No capability, namespace privilege, host administration, prior privileged setup, device configuration, or network access is required.

When CONFIG_CFI is disabled, the empty handler incorrectly consumes breakpoint type 0x03. When CONFIG_CFI is enabled, the handler can also consume the breakpoint when it originates from user mode. There is no race or timing requirement. The demonstrated consequence remains confined to incorrect userspace exception handling.

4. Primitive and severity interpretation

The exact defect is a logic error in ARM exception dispatch. A userspace breakpoint is incorrectly classified as handled instead of being returned through the unhandled-fault path.

There is no stale storage, active structured-object misuse, repeated release, refcount mutation, or memory corruption. PrimitiveClass is therefore NONE rather than Class B or Class C.

The demonstrated consequence is disruption of a debugger, runtime, or application that expects the breakpoint exception. Kernel crash, information disclosure, privilege escalation, authorization bypass, and cross-process impact are not established. ImportantCandidate is NO because there is no unresolved kernel-corruption or security-boundary primitive. AutoDowngradeAllowed is YES because the issue is a low-impact functional defect with no meaningful hidden exploitation leverage in the supplied evidence.

5. One-sentence report phrase

ARM breakpoint handling can incorrectly consume userspace breakpoint type 0x03, preventing delivery of the expected exception to the affected process without causing kernel memory corruption or crossing a security boundary.

6. Manual review recommendation

NO MANUAL CHECK NEEDED

The patch demonstrates a local userspace exception-handling error with no kernel crash, corruption, disclosure, authorization bypass, or privilege-escalation primitive.

7. Call-site confidence

Call-site confidence: high

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

Patch: ARM: 9481/2: breakpoint: CFI breakpoints only on demand [ Upstream
Commit: 22107402c2669b0163d43cc68901a2c4a59fa43a
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=22107402c2669b0163d43cc68901a2c4a59fa43a

Changed files:
  arch/arm/kernel/hw_breakpoint.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=22107402c2669b0163d43cc68901a2c4a59fa43a

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

The original Linux kernel CVE announcement for CVE-2026-90306 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90306

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:L/UI:N/S:U/C:N/I:N/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: 1

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).