[CVE-2026-46070][MODERATE REGULAR] md/raid5: validate payload size before accessing journal metadata

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

CVE: CVE-2026-46070
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: md/raid5: validate payload size before accessing journal metadata
Commit: 33698bd1b2db9764a29df7751533d33967ff5c98
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=33698bd1b2db9764a29df7751533d33967ff5c98
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46070
Analysis date: Wed, 27 May 2026 14:59:22 -0400
ActionableScore: 4
ActionableScore lower bound: 2
Actionable bucket: Borderline, manual review recommended
Manual review required: YES

Summary:
A corrupted md/raid5 r5cache journal can cause out-of-bounds reads during recovery because payload size fields are trusted before bounds validation, leading primarily to storage recovery failure or kernel DoS with limited paranoid C/I concern.

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ABOUT THIS REPORT
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The original Linux kernel CVE announcement for CVE-2026-46070 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46070

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.

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AL-KERNEL CLASSIFICATION RESULT
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CVE-2026-46070	MODERATE	CHECK	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:H/UI:N/S:U/C:L/I:L/A:H';CWE-125;*CWE-20;CWE-754;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '5.2';DESCR 'md raid5 r5cache recovery parses journal metadata payloads using size fields stored on disk. A corrupted or crafted journal can make a payload extend beyond the metadata block and cause out of bounds reads in r5c_recovery_analyze_meta_block() or r5l_recovery_verify_data_checksum_for_mb(). For the CVSS the PR:H is selected because reliable triggering normally requires administrative or block device level control over md raid journal metadata, or control of the underlying storage. The issue is not directly network reachable and is triggered during local RAID recovery or journal verification. Impact is at least denial of service via kernel crash or failed recovery. In the paranoid view, limited confidentiality or integrity impact is kept possible because this is an OOB read in kernel recovery code, but no controlled write or strong privilege escalation primitive is shown.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline, manual review recommended (with actual score 3)	YES	OOB DISK INIT LOG LINUS MEMORY  DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS_AND_CIANNH	NO	NO	guess

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ACTIONABLESCORE ANALYSIS
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ActionableScore=4
ActionableScoreLower=2

## 1. ActionableScore

* Conservative score: 2
* Paranoid score: 4
* Final recommended bucket: **Borderline, manual review recommended**::

## 2. Signal breakdown

Conservative signals:

* Reliable kernel crash / strong DoS: +1. Corrupted journal metadata can cause out-of-bounds reads during RAID5 r5cache recovery and may crash recovery or the kernel.
* Availability impact realistic: +1. The affected path is recovery / journal verification, so failure can block array recovery or cause a system-level storage DoS.
* Important filesystem/storage path: +1. This is md/raid5 journal recovery code, which is an important storage integrity and availability path.
* Firmware-mediated or storage-mediated external influence: +1. A malicious or corrupted underlying block device, disk image, or journal area can influence the parsed metadata, although this is not directly network reachable.
* Requires admin/root/block-device control in typical deployments: -2. Reliable triggering normally requires control over md RAID journal metadata, raw block device access, compromised storage, or administrative recovery setup.

Conservative total: 2

Paranoid additional signals:

* Confidentiality impact plausible: +1. The primitive is an OOB read in kernel recovery code, so limited adjacent memory exposure cannot be fully dismissed, although no read-back path is shown.
* Integrity impact plausible: +1. Recovery decisions are made from parsed journal metadata, so malformed metadata could theoretically influence recovery behavior, but no controlled write primitive is demonstrated.

Paranoid total: 4

Not counted:

* No generic memory corruption score. The patch supports OOB read / invalid read, not OOB write, UAF, double-free, heap overwrite, or arbitrary write.
* No privilege escalation score. There is no demonstrated reclaim, overwrite, object confusion, refcount takeover, or page-cache corruption primitive.
* No remote reachable score. The affected path is local storage recovery, not packet or network protocol parsing.

## 3. Reachability analysis

The bug is triggered when md/raid5 r5cache recovery parses corrupted or crafted journal metadata with payload sizes that exceed the remaining metadata block. In normal deployments, an attacker needs administrative control over the md device, raw block-device access, the ability to provide a malicious disk image, or control over underlying storage contents. Ordinary local unprivileged users generally cannot modify RAID journal metadata directly.

Namespaces and containers usually do not make this reachable unless the container is granted block-device access or powerful storage-management capabilities. The path is not network reachable by itself. Realistic exploitation is mainly a local privileged, compromised-storage, malicious-disk, or forensic-image recovery scenario.

## 4. Severity interpretation

This behaves more like a borderline / actionable Moderate storage bug than an Important-class vulnerability. The realistic impact is denial of service or failed RAID recovery due to invalid OOB reads while processing corrupted journal metadata. The theoretical concern is limited C/I impact from kernel OOB reads or recovery misinterpretation, but the patch does not show a write primitive, UAF, object lifetime corruption, or a credible LPE path.

Because the affected code is in an important storage recovery path and parses on-disk metadata, it should not be auto-closed without at least lightweight manual review. However, the need for block-device or storage-metadata control prevents this from being a strong Important candidate based on the provided evidence.

## 5. One-sentence report phrase

A corrupted md/raid5 r5cache journal can cause out-of-bounds reads during recovery because payload size fields are trusted before bounds validation, leading primarily to storage recovery failure or kernel DoS with limited paranoid C/I concern.

## 6. Manual review recommendation

MANUAL CHECK RECOMMENDED

Reason: this is an OOB read in an important kernel storage recovery path, but practical triggering normally requires privileged block-device or storage-metadata control and no strong privilege-escalation primitive is shown.

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

Patch: md/raid5: validate payload size before accessing journal metadata
Commit: 33698bd1b2db9764a29df7751533d33967ff5c98
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=33698bd1b2db9764a29df7751533d33967ff5c98

Commit description:

r5c_recovery_analyze_meta_block() and
r5l_recovery_verify_data_checksum_for_mb() iterate over payloads in a
journal metadata block using on-disk payload size fields without
validating them against the remaining space in the metadata block.

A corrupted journal contains payload sizes extending beyond the PAGE_SIZE
boundary can cause out-of-bounds reads when accessing payload fields or
computing offsets.

Add bounds validation for each payload type to ensure the full payload
fits within meta_size before processing.

Fixes: b4c625c ("md/r5cache: r5cache recovery: part 1")
Cc: stable@vger.kernel.org
Signed-off-by: Junrui Luo <moonafterrain@outlook.com>
Link: https://lore.kernel.org/linux-raid/SYBPR01MB78815E78D829BB86CD7C8015AF5FA@SYBPR01MB7881.ausprd01.prod.outlook.com/
Signed-off-by: Yu Kuai <yukuai@fnnas.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  drivers/md/raid5-cache.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=33698bd1b2db9764a29df7751533d33967ff5c98

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

The original Linux kernel CVE announcement for CVE-2026-46070 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46070

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:H/UI:N/S:U/C:L/I:L/A:H
  The Best / paranoid CVSS score: 5.2

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: 2
  Paranoid ActionableScore: 4

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).