[CVE-2026-74373][LOW] md/raid1,raid10: fix bio accounting for split md cloned bios [ Upstream

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

CVE: CVE-2026-74373
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: md/raid1,raid10: fix bio accounting for split md cloned bios [ Upstream
Commit: bb8d7ea74206b419aa05d7773a15a923b668c9f0
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=bb8d7ea74206b419aa05d7773a15a923b668c9f0
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74373
Analysis date: Sat, 15 Aug 2026 20:17:08 -0400
ActionableScore: 1
ActionableScore lower bound: unknown
Actionable bucket: Ordinary Moderate / Low-like
Manual review required: NO

Summary:
No one-sentence report phrase was found.

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

The original Linux kernel CVE announcement for CVE-2026-74373 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74373

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-2026-74373	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:L/A:N';CWE-682;CWE-703;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:N';BEST CVSS score: '2.5';DESCR 'md raid1 and raid10 could misclassify whether a bio is an md cloned bio during split bio resubmission on the read error path. This can cause double I/O accounting or missing I/O accounting for bios returned from bio_submit_split_bioset. The issue affects accounting correctness rather than memory safety. For the CVSS the PR:L is used for the paranoid case because a local user may be able to generate I/O on an existing md raid device, but reliable triggering still depends on a read error or recovery path. The issue is not network reachable. Impact is limited to inaccurate I/O accounting data and does not indicate kernel crash, memory corruption, information disclosure, or privilege escalation.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like (with actual score 1)	YES	DISK SIMPLEFIX ERRORPATH LINUS 	YES	NO	checked

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

ActionableScore=1

1. ActionableScore
* Conservative score: 1
* Paranoid score: 2
* Final recommended bucket: **Ordinary Moderate / Low-like**

2. Signal breakdown
* Important filesystem/storage path: +1. The code is in md raid1/raid10 block I/O handling, but the changed behavior is accounting-only.
* Local unprivileged trigger, paranoid only: +1. A local user may generate reads on a filesystem backed by md raid, but reliable triggering depends on an existing md device plus a read error and split-bio resubmission path.
* Hard or special condition: -1 for conservative interpretation. The bug requires failed bio handling and split resubmission, not ordinary I/O.
* No memory corruption signal. The patch does not show UAF, OOB access, double free, stale pointer reuse, refcount misuse, or object lifetime corruption.
* No reliable DoS signal. The described impact is double accounting or missing accounting, not panic, hang, device loss, or filesystem corruption.
* No confidentiality or integrity impact in the security sense. Incorrect I/O accounting may affect statistics, but no permission boundary or data modification primitive is shown.

3. Reachability analysis
A local workload can create I/O against an existing md raid1 or raid10 device, but the affected path requires a failed read bio that is split and resubmitted through bio_submit_split_bioset. Creating or configuring md raid devices normally requires administrative privileges, while merely issuing I/O may be possible for ordinary local users if they have access to files stored on the array. Namespaces do not materially lower the requirement unless the container is already given access to the md-backed storage. The path is not network reachable and not a default remote attack surface.

4. Severity interpretation
This behaves like an ordinary Low-like correctness issue rather than an actionable Moderate or Important kernel vulnerability. The patch fixes classification of md cloned bios for I/O accounting, not memory ownership, buffer bounds, page cache integrity, or bio lifetime. Theoretical impact is limited to inaccurate accounting on a rare error path. Realistic exploitation evidence for privilege escalation, information disclosure, persistent storage corruption, or reliable system-wide DoS is not present.

5. One-sentence report phrase
md raid1 and raid10 could incorrectly account split md cloned bios on a read error resubmission path, causing double or missing I/O accounting without evidence of memory corruption, privilege escalation, or reliable DoS.

6. Manual review recommendation
NO MANUAL CHECK NEEDED.
The issue is accounting correctness only, has no concrete memory corruption or crash primitive, is not network reachable, and the practical impact appears too low for urgent manual CVE handling.

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

Patch: md/raid1,raid10: fix bio accounting for split md cloned bios [ Upstream
Commit: bb8d7ea74206b419aa05d7773a15a923b668c9f0
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=bb8d7ea74206b419aa05d7773a15a923b668c9f0

Changed files:
  drivers/md/raid1.c
  drivers/md/raid10.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=bb8d7ea74206b419aa05d7773a15a923b668c9f0

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

The original Linux kernel CVE announcement for CVE-2026-74373 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74373

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:N
  The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:L/A:N
  The Best / paranoid CVSS score: 2.5

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).