[CVE-2026-64072][LOW] nvme: fix bio leak on mapping failure [ Upstream

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

CVE: CVE-2026-64072
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: nvme: fix bio leak on mapping failure [ Upstream
Commit: fea4b46f84c50caf93c6c0f2a54b1be2edfb4491
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=fea4b46f84c50caf93c6c0f2a54b1be2edfb4491
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64072
Analysis date: Sun, 19 Jul 2026 20:41:17 -0400
ActionableScore: 2
ActionableScore lower bound: 0
Actionable bucket: Ordinary Moderate / Low-like
Manual review required: NO

Summary:
A bio resource leak in the NVMe host ioctl error path can occur when integrity metadata mapping fails after request mapping, allowing a local actor with NVMe ioctl access to cause resource exhaustion through repeated failures.

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

The original Linux kernel CVE announcement for CVE-2026-64072 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64072

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-2026-64072	LOW	CHECK WITH IMPACT FROM ORIG NN MODERATE	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-401;*CWE-772;**CWE-400;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '4.7';DESCR 'A bio resource leak in the NVMe host ioctl path can occur when user request mapping succeeds but integrity metadata mapping fails. The error path checked a local bio variable that is always NULL, while the real bio is stored in req bio, so the request mapping was not released on this failure path. For the CVSS the PR:L reflects the paranoid case where a local untrusted user or service has delegated access to NVMe passthrough or block ioctls. The issue is not network reachable and requires local interaction with the NVMe device interface. Impact is denial of service via resource exhaustion after repeated failures, with no supported evidence of memory corruption, information disclosure, or privilege escalation.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like (with actual score 1)  SKIP CVE-2026-64072 UNKNOWN SKIP The Fixes patch not applied yet, so unlikely that actual: d0d1d522316e91f2b935a78bbf962b8e529d8c4f YES  NO NO unknown 	MAYBE	SIMPLEFIX NVME LEAK  DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_GUESSCVSS_AND_CIANNH	-	-	checked

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

ActionableScore=2
ActionableScoreLower=0

## 1. ActionableScore

* Conservative score: 0
* Paranoid score: 2
* Final recommended bucket: **Ordinary Moderate / Low-like**::

## 2. Signal breakdown

Conservative signals:

* Requires admin/root/CAP_* in typical deployments: -2. NVMe passthrough or similar block ioctl access is usually restricted to root, privileged services, or tightly controlled device-node permissions.
* Important filesystem/storage path: +1. The bug is in the NVMe host ioctl request mapping path, but it does not affect persistent metadata integrity or page cache ownership.
* Rare AND difficult-to-reach condition: -1. Trigger requires the integrity metadata mapping failure path after the main user request mapping succeeded.

Paranoid signals:

* Local unprivileged trigger: +1. Applies only if a local untrusted user or service has delegated access to the relevant NVMe device or passthrough ioctl.
* Availability impact realistic: +1. Repeated failures can leak bio resources and may eventually cause resource exhaustion.
* Important filesystem/storage path: +1. NVMe host request mapping is a storage path.
* Rare AND difficult-to-reach condition: -1. The integrity metadata failure condition is not a broad default path.

Not awarded:

* No generic memory corruption. The patch fixes a leak of req->bio on an error path, not UAF, double free, OOB write, type confusion, or arbitrary write.
* No privilege escalation plausible. There is no reclaim, stale callback, attacker-controlled overwrite, refcount takeover, or object confusion shown.
* No confidentiality or integrity impact. The leak affects resource lifetime, not data disclosure or unauthorized modification.
* No reliable strong DoS point. A single operation is not shown to crash or immediately disable the system.

## 3. Reachability analysis

The bug is reachable from a local NVMe host ioctl path when user request mapping succeeds and integrity metadata mapping later fails. In typical deployments, access to NVMe passthrough or raw block ioctls is restricted to root, administrative tools, or privileged service accounts, so the conservative interpretation does not treat it as unprivileged. A paranoid interpretation can use local PR:L if device access is delegated to a non-root service, container, or user in the disk group. The issue is not network reachable. The realistic exploitation condition is repeated local triggering of the failing metadata mapping path to accumulate leaked bio resources.

Call-site confidence: medium. The patch shows the relevant error path and object being leaked, but broader ioctl permission policy depends on deployment.

## 4. Severity interpretation

This behaves like an ordinary Moderate or Low-like resource leak rather than an Important kernel vulnerability. The theoretical worst case is local resource exhaustion after repeated failures, but the patch does not support memory corruption, privilege escalation, information disclosure, or persistent storage corruption. The issue should generally not be treated like an actionable Moderate unless the affected product delegates NVMe ioctl access to untrusted local users and the leak is easy to trigger repeatedly.

## 5. One-sentence report phrase

A bio resource leak in the NVMe host ioctl error path can occur when integrity metadata mapping fails after request mapping, allowing a local actor with NVMe ioctl access to cause resource exhaustion through repeated failures.

## 6. Manual review recommendation

NO MANUAL CHECK NEEDED

This is a constrained resource leak with no demonstrated memory corruption, no network reachability, and no plausible privilege escalation primitive in the provided patch context.

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

Patch: nvme: fix bio leak on mapping failure [ Upstream
Commit: fea4b46f84c50caf93c6c0f2a54b1be2edfb4491
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=fea4b46f84c50caf93c6c0f2a54b1be2edfb4491

Changed files:
  drivers/nvme/host/ioctl.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=fea4b46f84c50caf93c6c0f2a54b1be2edfb4491

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

The original Linux kernel CVE announcement for CVE-2026-64072 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64072

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:L
  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: 0
  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).