[CVE-2026-64060][LOW] netfs: Fix leak of request in netfs_write_begin() error handling [ Upstream

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

CVE: CVE-2026-64060
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: netfs: Fix leak of request in netfs_write_begin() error handling [ Upstream
Commit: 22ae28aae43623be235ff455558cdd13fbe2daeb
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=22ae28aae43623be235ff455558cdd13fbe2daeb
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64060
Analysis date: Sun, 19 Jul 2026 17:45:34 -0400
ActionableScore: 2
ActionableScore lower bound: 1
Actionable bucket: Ordinary Moderate / Low-like
Manual review required: NO

Summary:
A reference leak in `netfs_write_begin()` can occur when `netfs_wait_for_read()` fails, allowing a local writer on an affected netfs-backed filesystem to potentially cause gradual resource exhaustion, with no evidence of memory corruption or privilege escalation.

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

The original Linux kernel CVE announcement for CVE-2026-64060 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64060

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-2026-64060	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-401;*CWE-772;**CWE-400;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '4.7';DESCR 'A netfs request reference can leak in netfs_write_begin when netfs_wait_for_read returns an error before the request is released. A local process with write access to a file on an affected netfs based filesystem may be able to repeat the failing write begin path and gradually consume kernel memory or related request resources. For the CVSS the PR:L is used because reliable triggering requires a local user or process context that can access and write to the mounted filesystem, even if the underlying read failure may depend on network filesystem or storage error conditions. The issue is not directly network reachable as a packet only attack against the kernel. Impact is denial of service through resource exhaustion. There is no supported evidence of memory corruption, information disclosure, or privilege escalation from this patch context.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like (with actual score 2)	YES	REMOTE DISK SIMPLEFIX LEAK ERRORPATH LINUS 	YES	NO	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=2
ActionableScoreLower=1

## 1. ActionableScore

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

## 2. Signal breakdown

Triggered signals:

* **Local unprivileged trigger: +1**
  A local process with write access to an affected netfs-backed file may reach `netfs_write_begin()`.

* **Important filesystem/storage path: +1**
  The bug is in `fs/netfs/buffered_read.c`, in a page-cache/write-begin path used by network filesystem infrastructure.

* **Availability impact realistic: +1 paranoid only**
  In the worst case, repeated failures of `netfs_wait_for_read()` could leak request references repeatedly and cause resource exhaustion.

Negative signals:

* **Hard or unreliable triggering condition: -1**
  The leak requires an error from `netfs_wait_for_read()`, not just an ordinary write. Reliable exploitation likely depends on filesystem, server, cache, or I/O error conditions.

Not triggered:

* No generic memory corruption.
* No UAF, double-free, OOB write, refcount takeover, type confusion, or stale callback.
* No confidentiality or integrity primitive.
* No direct remote/network packet trigger.
* No privilege escalation evidence.

## 3. Reachability analysis

The likely trigger is a local process writing to a file on an affected netfs-based filesystem while the read-before-write path fails. This does not appear to be directly network-triggerable as a packet-only attack against the kernel. A remote filesystem server or network fault may help create the error condition, but a local write path is still needed for reliable triggering.

Namespaces and containers may matter only if an untrusted workload has write access to the affected mount. No special kernel memory-layout control is shown. The path is not a default global attack surface like TCP receive or netfilter packet processing.

Call-site confidence: **high**, because the changed call site and error path are visible in the patch.

## 4. Severity interpretation

This behaves like a **resource leak / availability-only Moderate or Low-like issue**, not an Important-class vulnerability. The theoretical worst case is sustained resource exhaustion if the failing path can be repeated many times. Realistic evidence supports a request reference leak, not memory corruption or privilege escalation.

The paranoid score is only slightly higher because repeated leaks can plausibly degrade availability, but the issue should not be escalated into memory corruption or LPE.

## 5. One-sentence report phrase

A reference leak in `netfs_write_begin()` can occur when `netfs_wait_for_read()` fails, allowing a local writer on an affected netfs-backed filesystem to potentially cause gradual resource exhaustion, with no evidence of memory corruption or privilege escalation.

## 6. Manual review recommendation

**NO MANUAL CHECK NEEDED**

This is a straightforward error-path reference leak with availability-only impact and no demonstrated corruption primitive. It can be handled as ordinary Moderate / Low-like unless product-specific evidence shows that repeated failures are easy to trigger at scale.

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

Patch: netfs: Fix leak of request in netfs_write_begin() error handling [ Upstream
Commit: 22ae28aae43623be235ff455558cdd13fbe2daeb
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=22ae28aae43623be235ff455558cdd13fbe2daeb

Changed files:
  fs/netfs/buffered_read.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=22ae28aae43623be235ff455558cdd13fbe2daeb

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

The original Linux kernel CVE announcement for CVE-2026-64060 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64060

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:L/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: 1
  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).