[CVE-2026-98269][MODERATE REGULAR] btrfs: abort transaction on failure to update inode for hole punching and reflinking [ Upstream

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

CVE: CVE-2026-98269
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: btrfs: abort transaction on failure to update inode for hole punching and reflinking [ Upstream
Commit: 2605eb9ba3bbd4c9f455cfe6b85bd28a1da7067d
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=2605eb9ba3bbd4c9f455cfe6b85bd28a1da7067d
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98269
Analysis date: Sat, 10 Oct 2026 16:29:45 -0400
ActionableScore: 4
ActionableScore lower bound: 3
Actionable bucket: Borderline / manual review recommended
Manual review required: YES

Summary:
No one-sentence report phrase was found.

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

The original Linux kernel CVE announcement for CVE-2026-98269 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98269

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: MODERATE REGULAR
Manual review required: YES

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
======================================================================

CVE-2026-98269	MODERATE	https://www.kernelcve.org/list/?q=CVE-2026-98269 CHECK WITH IMPACT FROM ORIG NN NONE | AEGIS IMPACT MODERATE AEGIS_AS=1 LEGACY=MODERATE RESULT=SAME (legacy and Aegis reconciliation agree; DECISION: both 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:H/A:H';CWE-703;CWE-754;CWE-459;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:H/A:L';BEST CVSS score: '6.3';DESCR 'A Btrfs transaction can remain eligible for commit after btrfs_update_inode fails during hole punching or reflinking, even though file extent items in the affected range have already been removed or replaced. Committing this partially updated transaction can create a persistent inconsistency between inode metadata and file extent metadata, potentially causing file corruption, data loss, filesystem check errors, or reduced filesystem availability. For the CVSS the PR:L value is used because a local user can normally request hole punching or reflinking for files that the user controls. Reliable triggering has high complexity because the attacker must also reach an error in btrfs_update_inode, which is generally dependent on filesystem state, resource pressure, or an underlying storage failure. The issue is not directly network reachable. The base impact is persistent integrity damage with limited availability impact. The paranoid impact allows high availability loss if committed metadata inconsistency makes the filesystem unusable or requires offline recovery.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline / manual review recommended (with actual score 4)	MAYBE	DISK INIT SIMPLEFIX SKIP  INCREASED_FROM_LOW_BASED_ON_REQUIREMANUALCHECK DECREASED_TO_MODERATEREG_BASED_ON_FALSEPOSCHECKOFKP	-	-	checked

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

ActionableScore=4
ActionableScoreLower=3
PrimitiveClass=CLASS_C
RealUAF=NO
HostAdminRequired=NO
NamespaceScopedPrivilege=NO
ImportantCandidate=NO
ManualReview=RECOMMENDED
AutoDowngradeAllowed=YES
RequiresHostUID0=NO
AuthorizationDecisionBypass=NO
ProtectedResourceImpact=NONE
B4PendingReview=NO
B4PendingConfirmed=NO

1. ActionableScore

* Raw conservative score: 3
* Conservative score: 3
* Raw paranoid score: 4
* Paranoid score: 4
* No floor or cap was applied.
* Final recommended bucket: **Borderline / manual review recommended**::

2. Signal breakdown

Conservative signals:

* +1 Local unprivileged trigger. An ordinary user can request hole punching or reflinking on files the user may modify. No administrative operation is required to enter the affected path.
* +1 Filesystem metadata corruption. Failure of `btrfs_update_inode()` can leave changed file extent items inconsistent with inode metadata if the transaction is later committed.
* +1 Important filesystem path. The defect affects Btrfs transaction consistency, extent mappings, and persistent on-disk metadata.
* +1 Integrity impact. The commit directly establishes a persistent inconsistency and therefore supports corruption or loss of data belonging to the affected file.
* -1 Corruption is constrained. No attacker-selected arbitrary metadata write, cross-file victim, shared-block ownership violation, or protected-file overwrite is established.

Paranoid-only signal:

* +1 Persistent availability risk. A committed on-disk inconsistency may require filesystem checking or offline recovery and can plausibly reduce filesystem availability. A filesystem shutdown or unmountable filesystem is not directly demonstrated.

Important non-awarded signals:

* No heap or slab OOB write is present. B5-R does not apply.
* No shared-backing or COW cross-authority write is established. B3-PENDING does not apply.
* No authorization decision changes from DENY to ALLOW. B4-PENDING does not apply.
* No UAF, stale reference, repeated release, refcount mutation, arbitrary write, controlled reclaim, or memory-corruption primitive is shown.
* No confidentiality impact, privilege escalation, cross-user file corruption, or remote reachability is established.
* Reliable kernel crash or filesystem shutdown was not awarded because the commit establishes persistent inconsistency, not a demonstrated panic or shutdown.

3. Reachability analysis

A local user can invoke hole punching or reflinking for a writable file through normal filesystem operations. The complete faulty outcome additionally requires `btrfs_update_inode()` to fail after extent metadata has already been changed and requires the transaction to be committed afterward. The user does not necessarily control that failure reliably, although resource pressure, filesystem state, or storage errors may supply it.

Host UID 0 and host-administrator capabilities are not required for the file operation itself. No namespace capability is involved, so this is not a namespace-scoped privilege path. A mounted affected Btrfs filesystem is a prerequisite, but no special hardware, boot mode, race, or prior privileged security-policy setup is identified. The issue is local rather than network-triggerable.

4. Primitive and severity interpretation

The exact primitive is a transaction-consistency failure. Modified file extent metadata can remain eligible for commit after the corresponding inode update fails. This is persistent filesystem invalid-state corruption rather than kernel memory corruption.

There is no stale object, UAF, OOB access, repeated lifetime operation, or active structured-object reuse. The appropriate classification is CLASS_C because the demonstrated behavior is persistent invalid filesystem state without an independently useful kernel-corruption or authorization primitive.

The demonstrated consequence is inconsistency between inode and extent metadata, with possible corruption or loss of data in the affected file. Reduced filesystem availability is a defensible paranoid consequence. Cross-file overwrite, arbitrary metadata modification, privilege escalation, and complete filesystem loss remain unsupported.

ImportantCandidate is NO because no ownership/COW violation, protected victim, memory-corruption primitive, or security-boundary bypass is established. AutoDowngradeAllowed is YES because the issue remains a constrained filesystem consistency defect, although manual review is recommended due to persistent on-disk impact.

5. One-sentence report phrase

A failed Btrfs inode update during hole punching or reflinking can leave partially modified extent metadata eligible for commit, causing persistent file metadata inconsistency and possible data corruption or recovery-related filesystem unavailability.

6. Manual review recommendation

MANUAL CHECK RECOMMENDED

Persistent on-disk inconsistency warrants review, but the supplied evidence does not establish memory corruption, cross-file ownership violation, authorization bypass, or Important-grade exploitation leverage.

7. Call-site confidence

Call-site confidence: medium

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

Patch: btrfs: abort transaction on failure to update inode for hole punching and reflinking [ Upstream
Commit: 2605eb9ba3bbd4c9f455cfe6b85bd28a1da7067d
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=2605eb9ba3bbd4c9f455cfe6b85bd28a1da7067d

Changed files:
  fs/btrfs/file.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=2605eb9ba3bbd4c9f455cfe6b85bd28a1da7067d

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

The original Linux kernel CVE announcement for CVE-2026-98269 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98269

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:H/A:L
  The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:H/A:H
  The Best / paranoid CVSS score: 6.3

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: 3
  Paranoid ActionableScore: 4

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: MODERATE
KPANIC detected for this report: NO
Published priority for this report (same as in Subject): MODERATE REGULAR

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).