[CVE-2026-46169][MODERATE 7.0] hfsplus: fix uninit-value by validating catalog record size [ Upstream

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

CVE: CVE-2026-46169
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: hfsplus: fix uninit-value by validating catalog record size [ Upstream
Commit: 61a790974ff7e533acbceca06c7d02f22bf96d4d
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=61a790974ff7e533acbceca06c7d02f22bf96d4d
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46169
Analysis date: Thu, 28 May 2026 11:13:55 -0400
ActionableScore: 5
ActionableScore lower bound: 3
Actionable bucket: Actionable Moderate at minimum
Manual review required: NO

Summary:
Malformed HFS Plus catalog records can be accepted with a shorter than expected on-disk size, leaving catalog entry fields uninitialized and causing invalid reads or kernel crashes during catalog name handling.

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

The original Linux kernel CVE announcement for CVE-2026-46169 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46169

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: NO

A detailed explanation of the methodology and priority rules is included
at the end of this message.

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AL-KERNEL CLASSIFICATION RESULT
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CVE-2026-46169	MODERATE	CHECK	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:N/A:H';*CWE-457;CWE-908;CWE-125;*CWE-20;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:L/I:N/A:H';BEST CVSS score: '6.3';DESCR 'HFS Plus catalog parsing could accept a short on disk catalog record and leave parts of the catalog entry structure uninitialized. The uninitialized nodeName data can later be used during key construction and string comparison, including as input to case folding logic, which can lead to invalid reads or kernel crash when a corrupted filesystem is mounted or accessed. For the CVSS the PR:L is used for the paranoid score because a reduced privilege local user may provide a crafted filesystem image or removable media in automount or delegated mount environments, even though the base case usually requires administrative mount privileges. The issue is not network reachable. Impact is mainly local denial of service, with possible kernel information disclosure from uninitialized data use and no supported write primitive or direct privilege escalation path.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 4)  SKIP CVE-2026-46169  SKIP No affected files built, so skip this CVE NO  - - unknown 	MAYBE	KASAN DISK WARNONLY LOG IMPROVEONLY SYZBOT  INCREASED_FROM_LOW_BASED_ON_REQUIREMANUALCHECK DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5	-	-	checked

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

ActionableScore=5
ActionableScoreLower=3

## 1. ActionableScore

* Conservative score: 3
* Paranoid score: 5
* Final recommended bucket: **Actionable Moderate at minimum**::

## 2. Signal breakdown

Conservative signals:

* Weak/indirect corruption candidate: +1. A short catalog record can leave parts of `hfsplus_cat_entry` uninitialized, and later code uses that data in string comparison and case folding.
* Reliable kernel crash / strong DoS: +1. KMSAN reported uninitialized value use, and malformed records can plausibly crash during mount or lookup.
* Confidentiality impact plausible: +1. Uninitialized kernel stack or heap bytes may influence copied name data and comparison paths.
* Important filesystem/storage path: +1. This is catalog metadata parsing in a filesystem driver.
* Requires admin/root mount in typical deployments: -2. Mounting arbitrary HFS Plus images normally requires `CAP_SYS_ADMIN`.

Paranoid additional signals:

* Local unprivileged trigger: +1. In desktop, removable media, automount, or delegated mount environments, a reduced privilege user may supply a crafted HFS Plus image.
* Filesystem metadata corruption reachable by local user: +1. The trigger is malformed on-disk catalog metadata.
* Availability impact realistic: +1. Crafted filesystem access can cause invalid reads or crash.
* Constrained primitive: -1. The patch supports uninitialized reads and invalid/OOB read risk, not an arbitrary write or UAF primitive.

## 3. Reachability analysis

The attacker needs to provide a corrupted HFS Plus filesystem image or removable medium and cause it to be mounted or accessed. In a conservative server model this requires administrative mount privileges, but in desktop or containerized environments automount or delegated mount policies can lower the practical privilege requirement.

This is not network reachable by itself. The bug is triggered by filesystem metadata parsing during mount, lookup, or catalog access.

## 4. Severity interpretation

This behaves like actionable Moderate in environments where untrusted filesystem images can be mounted or auto-mounted. The realistic impact is local DoS and possible limited kernel information disclosure through uninitialized data use.

It does not currently behave like an Important memory-corruption issue because the patch does not show a write primitive, UAF, double free, or direct privilege escalation path.

## 5. One-sentence report phrase

Malformed HFS Plus catalog records can be accepted with a shorter than expected on-disk size, leaving catalog entry fields uninitialized and causing invalid reads or kernel crashes during catalog name handling.

## 6. Manual review recommendation

MANUAL CHECK RECOMMENDED

Review mount and automount exposure. If only trusted root can mount HFS Plus images, priority is lower. If untrusted users can provide removable media or filesystem images, this should not be auto-closed.

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

Patch: hfsplus: fix uninit-value by validating catalog record size [ Upstream
Commit: 61a790974ff7e533acbceca06c7d02f22bf96d4d
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=61a790974ff7e533acbceca06c7d02f22bf96d4d

Changed files:
  fs/hfsplus/bfind.c
  fs/hfsplus/catalog.c
  fs/hfsplus/dir.c
  fs/hfsplus/hfsplus_fs.h
  fs/hfsplus/super.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=61a790974ff7e533acbceca06c7d02f22bf96d4d

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

The original Linux kernel CVE announcement for CVE-2026-46169 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46169

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:L/I:N/A:H
  The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:N/A:H
  The Best / paranoid CVSS score: 6.3

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: NO
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).