[CVE-2026-64232][LOW] block: recompute nr_integrity_segments in blk_insert_cloned_request [ Upstream

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

CVE: CVE-2026-64232
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: block: recompute nr_integrity_segments in blk_insert_cloned_request [ Upstream
Commit: 53a01bcc0242590eda4c452a5bd996f62457113b
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=53a01bcc0242590eda4c452a5bd996f62457113b
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64232
Analysis date: Fri, 24 Jul 2026 12:33:35 -0400
ActionableScore: 2
ActionableScore lower bound: unknown
Actionable bucket: Ordinary Moderate / Low-like
Manual review required: NO

Summary:
A local user able to submit I/O through an already configured stacked block device with integrity metadata may trigger incorrect integrity segment accounting in blk_insert_cloned_request(), causing a BUG_ON during dispatch and resulting in a kernel crash.

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

The original Linux kernel CVE announcement for CVE-2026-64232 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64232

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.

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AL-KERNEL CLASSIFICATION RESULT
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CVE-2026-64232	LOW	CHECK WITH IMPACT FROM ORIG NN LOW	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H';CWE-682;CWE-617;CWE-754;BEST CVSS score: '4.7';DESCR 'blk_insert_cloned_request could reuse a cached nr_integrity_segments value from the upper request even though the lower queue may have stricter segment limits. In stacked block setups with integrity metadata, such as dm multipath over nvme rdma, the real integrity segment count can be higher than the cached value and blk_rq_map_integrity_sg can hit BUG_ON during dispatch. For the CVSS the PR:L because a local user or process that can submit I/O to an already configured vulnerable block stack may be able to trigger the faulty dispatch path without administrator level mount or device setup privileges. The issue is not directly network reachable even if the underlying storage transport is nvme rdma, because the trigger is local block I/O through a preconfigured stack. Impact is denial of service via kernel BUG or panic, with no supported evidence of information disclosure or privilege escalation.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like (with actual score 2)	YES		YES	NO	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=2

## 1. ActionableScore

* Conservative score: 2
* Paranoid score: 2
* Final recommended bucket: **Ordinary Moderate / Low-like**::

## 2. Signal breakdown

Triggered signals:

* Local unprivileged trigger: +1
  A local user or process that can submit I/O through an already configured vulnerable stacked block device may be able to reach the dispatch path.

* Reliable kernel crash / strong DoS: +1
  The commit describes a direct BUG_ON in blk_rq_map_integrity_sg() when integrity segment accounting is too low.

* Important filesystem/storage path: +1
  The affected code is in the block layer request dispatch path and may affect stacked storage configurations.

Subtracting signals:

* Rare AND difficult-to-reach subsystem/configuration: -1
  Triggering requires blk-integrity metadata plus a stacked setup with differing queue limits, such as dm-multipath over nvme-rdma. This is not a default common desktop or generic server path.

Not triggered:

* No remote reachable signal. nvme-rdma may be part of the backend storage transport, but the vulnerable trigger is local block I/O through a configured stack.
* No generic memory corruption signal. The patch prevents a BUG_ON due to incorrect segment accounting, not a UAF, OOB write, double free, or object lifetime primitive.
* No privilege escalation signal. There is no supported reclaim, overwrite, refcount takeover, type confusion, or page-cache corruption primitive.
* No confidentiality or integrity impact signal.

Call-site confidence: high. The commit directly identifies blk_rq_map_integrity_sg() as the BUG_ON consumer of the stale nr_integrity_segments value.

## 3. Reachability analysis

The realistic trigger is local I/O submitted to a preconfigured stacked block device that uses integrity metadata. A normal unprivileged user may be able to trigger it if they can write or otherwise generate I/O through a filesystem or block device backed by the affected stack, but creating the dm-multipath or nvme-rdma setup itself normally requires administrative privileges.

Namespaces and containers do not strongly increase reachability unless a container is given access to the affected block device or filesystem. The path is not directly network reachable. The nvme-rdma example is storage-transport related, not an unauthenticated remote network parser.

The practical conditions are specific: integrity metadata must be present, the request must be cloned through a stacked driver, and the lower queue must require more integrity segments than the cached value inherited from the upper request.

## 4. Severity interpretation

This behaves like an ordinary Moderate or Low-like kernel DoS. The failure mode is a reliable BUG_ON under specific storage configuration conditions, but the patch does not show memory corruption, data corruption, privilege escalation, or a confidentiality primitive.

The theoretical impact is a local host crash. Realistic exploitation evidence supports availability impact only.

## 5. One-sentence report phrase

A local user able to submit I/O through an already configured stacked block device with integrity metadata may trigger incorrect integrity segment accounting in blk_insert_cloned_request(), causing a BUG_ON during dispatch and resulting in a kernel crash.

## 6. Manual review recommendation

NO MANUAL CHECK NEEDED

This can be handled as a DoS-only block-layer accounting bug unless the affected product heavily relies on blk-integrity with stacked storage such as dm-multipath over nvme-rdma.

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

Patch: block: recompute nr_integrity_segments in blk_insert_cloned_request [ Upstream
Commit: 53a01bcc0242590eda4c452a5bd996f62457113b
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=53a01bcc0242590eda4c452a5bd996f62457113b

Changed files:
  block/blk-mq.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=53a01bcc0242590eda4c452a5bd996f62457113b

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

The original Linux kernel CVE announcement for CVE-2026-64232 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64232

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: Not available
  The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS score: 4.7

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: 2

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).