[CVE-2026-92494][LOW] ext4: fix buffer_head leak in ext4_init_orphan_info [ Upstream

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

CVE: CVE-2026-92494
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: ext4: fix buffer_head leak in ext4_init_orphan_info [ Upstream
Commit: a9a6ec1298f9bc134b2c5db27d25bb10603b7113
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=a9a6ec1298f9bc134b2c5db27d25bb10603b7113
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-92494
Analysis date: Fri, 18 Sep 2026 02:12:37 -0400
ActionableScore: 1
ActionableScore lower bound: unknown
Actionable bucket: Ordinary Moderate
Manual review required: NO

Summary:
No one-sentence report phrase was found.

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

The original Linux kernel CVE announcement for CVE-2026-92494 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-92494

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-2026-92494	LOW	https://www.kernelcve.org/list/?q=CVE-2026-92494 CHECK WITH IMPACT FROM ORIG NN LOW	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H';*CWE-401;*CWE-772;**CWE-400;Other CVSS 'AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '4.4';DESCR 'A buffer_head reference leak in ext4_init_orphan_info() can occur when an ext4 orphan file block is read successfully but then fails bad magic/checksum validation. The error path previously skipped the current buffer_head and released only earlier entries, leaving a kernel reference leaked after the failed mount path. For the CVSS the PR:H is used because reliable triggering normally requires the ability to mount or supply a crafted ext4 filesystem image on the target. The issue is not network reachable and does not indicate a UAF, OOB access, or arbitrary write primitive. Impact is denial of service through gradual kernel memory/resource exhaustion after repeated mount attempts, not privilege escalation.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 1)	YES	DISK SIMPLEFIX LEAK ERRORPATH LINUS 	YES	NO	checked

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

ActionableScore=1
PrimitiveClass=NONE
RealUAF=NO
HostAdminRequired=YES
NamespaceScopedPrivilege=NO
ImportantCandidate=NO
ManualReview=NO
AutoDowngradeAllowed=YES

1. ActionableScore

* Raw conservative score: 1
* Conservative score: 1
* Raw paranoid score: 1
* Paranoid score: 1
* Final recommended bucket: **Ordinary Moderate**::

No floor or cap changed the score.

2. Signal breakdown

Positive signals:

* +1 Concrete persistent kernel resource/reference leak. `ext4_bread()` returns a `buffer_head` reference and the old error path skipped the currently loaded entry after bad magic or checksum validation failed.
* +1 Resource exhaustion potential. Repeated failed mount attempts against a malformed ext4 filesystem with orphan file blocks could accumulate leaked `buffer_head` references.
* +1 Important filesystem/storage path. The code is in ext4 orphan file initialization during mount, but the established defect is still a reference leak rather than filesystem ownership corruption or metadata overwrite.

Negative signals:

* -2 Host-admin-equivalent triggering requirement. Reliable triggering normally requires mounting or providing a crafted ext4 filesystem image to the kernel, which is host-admin-controlled in normal Linux deployments.

Non-awarded signals:

* No UAF or double release is established.
* No OOB read or OOB write is established.
* No arbitrary write or controlled reclaim is demonstrated.
* No confidentiality or integrity impact is awarded.
* No security-boundary bypass is established.
* No remote reachability is established.
* No extra availability point is awarded beyond the resource-exhaustion potential.

3. Reachability analysis

The practical trigger is a malformed ext4 filesystem whose orphan file block is read successfully but fails magic or checksum validation. A local attacker would normally need host-admin-equivalent ability to mount the crafted filesystem image or otherwise make the host mount it. The complete trigger is not shown to be namespace-scoped because ext4 mounting is not generally available to ordinary unprivileged users inside attacker-created namespaces. There is no network path in the patch. No race or special timing is required. No special hardware is required.

4. Primitive and severity interpretation

The exact primitive is a leaked `buffer_head` reference on an ext4 mount error path. This is a resource/reference leak, not stale post-lifetime use. The skipped object is not used after free, and the patch does not show a second `brelse()` on the same dangling object. The demonstrated consequence is gradual kernel resource or memory pressure if the failing path is repeated. The speculative worst case is local DoS through exhaustion, but there is no supported path to privilege escalation, information disclosure, arbitrary write, or filesystem ownership bypass.

PrimitiveClass is NONE because no meaningful corruption, lifetime misuse after free, authorization bypass, or ownership violation is established. ImportantCandidate is NO because the issue is host-admin-gated and resource-leak-only. AutoDowngradeAllowed is YES because no unresolved kernel-corruption or security-boundary primitive remains.

5. One-sentence report phrase

A buffer_head reference leak in ext4_init_orphan_info can occur on malformed orphan file blocks and may cause gradual local resource exhaustion after repeated privileged mount attempts, but it does not establish memory corruption, privilege escalation, or network reachability.

6. Manual review recommendation

NO MANUAL CHECK NEEDED

Reason: this is a concrete but narrow resource/reference leak with host-admin-gated reachability and no UAF, OOB access, arbitrary write, authorization bypass, or plausible LPE primitive.

7. Call-site confidence

Call-site confidence: high

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

Patch: ext4: fix buffer_head leak in ext4_init_orphan_info [ Upstream
Commit: a9a6ec1298f9bc134b2c5db27d25bb10603b7113
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=a9a6ec1298f9bc134b2c5db27d25bb10603b7113

Changed files:
  fs/ext4/orphan.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=a9a6ec1298f9bc134b2c5db27d25bb10603b7113

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

The original Linux kernel CVE announcement for CVE-2026-92494 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-92494

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:L/PR:H/UI:N/S:U/C:N/I:N/A:L
  The Best / paranoid CVSS vector: AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS score: 4.4

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).