[CVE-2026-45960][MODERATE REGULAR] hfsplus: return error when node already exists in hfs_bnode_create [ Upstream

[CVE-2026-45960][MODERATE REGULAR] hfsplus: return error when node already exists in hfs_bnode_create [ Upstream

[AL-KERNEL]

CVE: CVE-2026-45960
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: hfsplus: return error when node already exists in hfs_bnode_create [ Upstream
Commit: 1ca428769cb4737a25bd32fb4d1573cc09eeaeef
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=1ca428769cb4737a25bd32fb4d1573cc09eeaeef
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-45960
Analysis date: Wed, 27 May 2026 19:20:38 -0400
ActionableScore: 3
ActionableScore lower bound: unknown
Actionable bucket: Borderline, manual review recommended
Manual review required: YES

Summary:
No one-sentence report phrase was found.

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

The original Linux kernel CVE announcement for CVE-2026-45960 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-45960

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 REGULAR
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-2026-45960	MODERATE	CHECK	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:H';CWE-911;CWE-617;*CWE-20;*CWE-664;Other CVSS 'AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '6.6';DESCR 'hfs_bnode_create() could return an already hashed HFS plus btree node without taking a new reference, creating inconsistent refcount state. A crafted or corrupted HFS plus image can make later hfs_bnode_put() hit a BUG_ON() when the node refcount is already zero, causing a kernel panic. For the CVSS the PR:L is used in the paranoid score because a local user may trigger operations once the crafted filesystem is mounted, although direct mounting usually requires administrator privileges. The issue is not network reachable. Impact is primarily denial of service, with limited confidentiality and integrity concern only from the refcount inconsistency in filesystem metadata handling.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline, manual review recommended (with actual score 3) 	MAYBE	DISK UAF IMPROVEONLY LINUS SYZBOT  DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5	-	-	checked

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

ActionableScore=3

1. ActionableScore
* Conservative score: 3
* Paranoid score: 3
* Final recommended bucket: **Borderline, manual review recommended**::

2. Signal breakdown
* Filesystem/storage metadata corruption reachable after mount: +1. A corrupted HFS+ image can create inconsistent btree node/refcount state.
* Reliable kernel crash / DoS: +1. The described path hits `BUG_ON(!atomic_read(&node->refcnt))` in `hfs_bnode_put()`.
* Important filesystem path: +1. The issue is in HFS+ btree node creation/allocation.
* Weak refcount/lifetime concern: +1. Returning an already hashed node without taking a reference creates a refcount inconsistency, but no UAF reclaim or controlled overwrite is shown.
* Requires admin/root to mount in typical deployments: -2. Direct mounting of crafted HFS+ images normally requires `CAP_SYS_ADMIN`.
* Paranoid lower-privilege trigger caveat. If the image is auto-mounted or mounted by a helper, a local user may trigger operations afterward, but that is deployment dependent.

3. Reachability analysis
The main trigger is a crafted or corrupted HFS+ filesystem image where allocation metadata allows an already-used btree node to be allocated again. Direct mounting is typically privileged. Exposure increases on systems with automount, removable-media workflows, or delegated mount helpers. Once mounted, ordinary file operations may reach the faulty path. It is not network reachable.

4. Severity interpretation
This is more than a simple warning because it creates a refcount inconsistency in filesystem btree metadata, but the demonstrated result is kernel panic via BUG_ON. No memory corruption primitive, information leak, arbitrary write, or privilege escalation is demonstrated. It is borderline and worth manual awareness mainly due to filesystem metadata/lifetime semantics.

5. One-sentence report phrase
A crafted HFS+ image can make `hfs_bnode_create()` return an already hashed btree node without a new reference, causing refcount inconsistency and kernel panic during later node release.

6. Manual review recommendation
MANUAL CHECK RECOMMENDED. The issue is crafted-filesystem metadata/refcount inconsistency with reliable DoS, but no proven memory-corruption exploit or LPE path.

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

Patch: hfsplus: return error when node already exists in hfs_bnode_create [ Upstream
Commit: 1ca428769cb4737a25bd32fb4d1573cc09eeaeef
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=1ca428769cb4737a25bd32fb4d1573cc09eeaeef

Changed files:
  fs/hfsplus/bnode.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=1ca428769cb4737a25bd32fb4d1573cc09eeaeef

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

The original Linux kernel CVE announcement for CVE-2026-45960 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-45960

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:H/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS vector: AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:H
  The Best / paranoid CVSS score: 6.6

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: 3

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: NO
Published priority for this report (same as in Subject): MODERATE REGULAR

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).